yeah in hindsight you're correct and my original post was lacking nuance. i wrote it rather quickly in reaction to a common phenomenon i see in the fandom, which is to attribute the first siege of the burial mounds solely to wei wuxian's class while not taking into account at all the fact that he did kill a bunch of people.
i also agree that the question you bring up - whose acts of violence are sanctioned by society, and whose are not - is arguably one of the central themes of MDZS. this is especially true in the case of xue yang, as his entire arc is built around this question. as you pointed out, other character (eg. jin guangyao) are allowed to wipe out entire sects with society's full approval, but xue yang doing the same is not socially sanctioned in the same way. and the maiming of xue yang's body, which prompted a lot of xue yang's future violence, would have been unacceptable had it happened to a higher-status character, underscoring the theme that not all acts of the same violence, targets of the same violence, and perpetrators of the same violence are made equal in society's eyes.
that said, one thing i really admire about the writing of MDZS is that it does not make the background characters idiots. there are in fact no shortage of stories about a sad misunderstood protagonist, who due to various reasons - including societal prejudice - is unfairly maligned and persecuted by society; these stories, however, often rely on the background characters perpetrating this persecution to be complete idiots. in order for these stories to work, the background characters often have to have an irrational hatred of the main character that borders on obsessive, such that they will go to ridiculous lengths to ruin the main character's life over literally nothing, even though realistically most people have better things to do with their lives. in order for these stories to work, the background characters also often have to be incredibly stupid, such that they can directly witness the main character being virtuous or harmless and still believe some random antagonist going "but he's Bad!" with zero evidence.
such stories, which makes the average person inside of it a complete moron, are dogshit. happily, though, MDZS is a better-written work, and thus does not suffer from the same problem. one of the smartest things about MDZS is that, if you analyze the story based on what information the average outside observer would have access to, the logic that leads them to the first siege of the burial mounds is reasonable.
as an outside observer, this is all of the information you have access to about the background leading up to the qiongqi pass massacre:
during the sunshot campaign, wei wuxian invents demonic cultivation. he uses it to raise the dead and use them to win the war against the wen.
after the war, wei wuxian continues to use demonic cultivation, refusing to return to the path of righteous cultivation or even carry his sword. he continues to use his demonic cultivation in flashy ways at public events (eg. claiming 1/3 of the prey at the phoenix mountain nighthunt). as a result, demonic cultivator hopefuls start cropping up, hoping to learn this heretical, corpse-desecrating cultivation from him. wei wuxian does nothing to dissuade these people.
furthermore, wei wuxian does not heed the words of his sect leader, and instead openly disrespects him.
wei wuxian crashes a jin party he was not invited to and accuses jin zixun of abusing the wen prisoners under the latter's purview. when jin zixun refuses to tell wei wuxian where wen ning is, wei wuxian threatens to kill everyone gathered ("if i wanted to kill everyone here, who could stop me? who dares stop me?").
upon learning that wen ning is at a labor camp in the qiongqi pass, wei wuxian kills 4 of the supervisors there, escapes with the wen prisoners, and sets up camp in the burial mounds.
wei wuxian's sect leader, jiang wanyin, challenges wei wuxian's actions; this results in a physical fight between the two and yunmeng jiang severing all political ties with wei wuxian.
wei wuxian refines wen ning into the world's most powerful fierce corpse in existence, a feat never before seen in the cultivation world.
wei wuxian continues to publicly use his demonic cultivation, which includes bringing his one-of-a-kind and incredibly powerful fierce corpse with him on nighthunts. as a result, more demonic cultivator hopefuls gather in yiling, hoping to learn demonic cultivation from wei wuxian.
here, there is plenty of room for classism and other prejudices to bias an outside observer against wei wuxian. for example, in #3 of the first list, if wei wuxian had been nobly born (instead of the son of wei changze, jiang fengmian's former servant), then people would probably not gossip about him not respecting his sect leader in the same way that they did in canon. furthermore, had wei wuxian been nobly born, then it is possible that the public would not have viewed his continued usage of demonic cultivation in as negative a light, either (#2 on the list): for example, maybe they would not have seen him claiming 1/3 of the prey at the phoenix mountain nighthunt as an arrogant move in the same way they did in canon, given that nie mingjue also claimed an entire third and no one had any complaints about that.
furthermore, had wei wuxian been nobly born, then it is possible that the public would not have as much of an issue with him publicly challenging jin guangshan and lanling jin on the issue of the wen prisoners. from the narration, it seems that part of the reason why the public takes issue with wei wuxian publicly challenging jin guangshan in this matter is because they view it as wei wuxian, the son of a servant, disrespecting a social better. however, it must be noted that this event happened during a time when yunmeng jiang was very weak, and yunmeng jiang was not invited at all to the party that wei wuxian crashed - a sign of disrespect. thus, even if wei wuxian had been nobly born, it is likely that the public still would have had a problem with wei wuxian challenging jin guangshan and comparing him to wen ruohan, because of yunmeng jiang's weakness as compared to lanling jin.
however, it must be noted that, during the time period of the first list above, classism was not the only bias turning people against wei wuxian. one of the problems people had with wei wuxian was his usage of demonic cultivation (which they did not think of as "ghost cultivation," regardless of whether or not that was what it actually was) itself, because the demonic cultivation itself was already viewed as heretical. even if wei wuxian had been nobly born, his continued open usage of demonic cultivation would still have been viewed as a problem. this bias against demonic cultivation actually has very little to do with classism (no matter how many pseudoacademic essays one might see about demonic cultivation being "democratic" lmao), because the cultural taboo against desecrating the dead has nothing to do with class (and in fact, historically speaking, things were often the other way around: the bodies of the poor get desecrated, while the bodies of the rich do not). keep in mind that this was the same era in which wei wuxian was puppetting around the corpses of dead women to fawn over him - how would you feel if that was the corpse of your daughter, your sister, yourself? did she consent to have her body be used in that way?
furthermore, wei wuxian's open usage of demonic cultivation was inspiring other people to want to learn demonic cultivation as well. even before wei wuxian left yunmeng jiang, demonic cultivation hopefuls were already seeking to learn demonic cultivation from wei wuxian, and from the point of view of the public wei wuxian did not do enough to dissuade them. and this in fact was a massive problem, as it meant more people were being swayed off what society considered to be the righteous path.
the other non-classist prejudice that biased people against wei wuxian was anti-wen bias. this is notably not classism: before the sunshot campaign, qishan wen was the most powerful sect in the cultivation world. the wen remnants are not commoners; they are fallen nobility. the remaining wen being persona non grata postwar has nothing to do with classism and instead has everything to do with the atrocities the sect the public associates with them, qishan wen, committed before the war. anti-wen prejudice is not at all comparable to classism; instead, it is best compared to anti-japanese sentiment in china after the second sino-japanese war, during which japan committed numerous war crimes against the chinese civilian populace.
therefore, the above list of information that the public could be reasonably expected to have about wei wuxian leaves plenty of room for prejudices to bias an outside observer against wei wuxian. however, of those prejudices, only one is classism; non-classist prejudices such as bias against demonic cultivation and bias against the wen would have also done a lot of heavy lifting in biasing an outside observer against wei wuxian.
meanwhile, this is all the information you have access to about the events of the qiongqi pass massacre and afterwards:
wei wuxian's former shijie jiang yanli, as well as her husband jin zixuan, invite wei wuxian to their son's 100-day celebration. wei wuxian goes to attend this celebration, bringing his fierce corpse, wen ning, with him.
jin zixun accuses wei wuxian, a demonstrated demonic cultivator, of casting the hundred holes curse on him. as a result, he and a group of around 200 jin cultivators confront wei wuxian in the qiongqi pass while the latter is on his way to the celebration.
jin zixuan attempts to defuse the situation but is killed by wen ning, wei wuxian's fierce corpse.
wen ning then kills everyone else gathered as well.
jin guangshan issues a statement saying that he is willing to let this matter go if wen qing and wen ning turn themselves in.
wen qing and wen ning go to jinlintai. however, once there, wen ning kills another 20-30 cultivators, which includes not just jin cultivators but also cultivators from the lan and the nie.
as a result of this, jin guangshan calls for a gathering at nightless city to discuss the question of what to do with wei wuxian.
at the nightless city pledge conference, jin guangshan says that the earlier deal is off and declares war on wei wuxian and the remaining escaped wen prisoners.
wei wuxian then shows up to the pledge conference and starts a verbal argument with the gathered cultivators.
one of the cultivators present shoots wei wuxian. in retaliation, wei wuxian raises the corpses in nightless city and starts massacring everyone.
the outcome of this is that anywhere from 10-3000 people are killed, including wei wuxian's former shijie jiang yanli.
my Hot Take of the day is that:
if the above information is all an observer has access to, then it is entirely reasonable for the observer to conclude that the first siege is necessary.
if wei wuxian had been nobly born instead of the son of a servant, the cultivation world would have reacted to the above events in the exact same way. classism no longer factors into the conversation.
because - let's be real here - this sequence of events makes wei wuxian look really bad. an outside observer does not know that wei wuxian lost control of his one-of-a-kind ultra-powerful fierce corpse (which up until now wei wuxian has never lost control of), so it's more reasonable for an outside observer to conclude that everything wen ning did, wei wuxian deliberately ordered wen ning to do. once this assumption is made, all of the above events look really bad.
wei wuxian arguing with jin zixun about the hundred holes curse? reasonable if wei wuxian actually didn't cast the curse. wei wuxian killing jin zixuan? pretty bad, considering that jin zixuan 1. was trying to defuse the situation; 2. is the heir of lanling jin; and 3. is the husband of wei wuxian's ex-shijie. wei wuxian then killing all 200+ people gathered there? unnecessary overkill.
wen ning and wen qing saying they would turn themselves in, only for wen ning to then kill another 20-30 people at jinlintai once they let him in? this is the big one. this looks really fucking bad. an outside observer has zero reason to believe that wen ning was not acting on wei wuxian's orders when he did this - they don't know that wen qing froze wei wuxian in the burial mounds with her needles, or even that wen ning was capable of making decisions that went against wei wuxian's wishes. thus, the most reasonable conclusion for an outside observer to come to is that wei wuxian deliberately ordered wen ning to pretend to surrender so he could kill more people in jinlintai. this sort of "i surrender, suckers" maneuver is viewed poorly even by modern standards (and perfidy is considered a war crime), so it is entirely reasonable that this maneuver would make wei wuxian look terrible to outside observers.
due to this perceived perfidy, jin guangshan reneging on his previous promise to leave the wen prisoners out of the matter would be viewed by the public as harsh, but reasonable. as would jin guangshan calling for the nightless city pledge conference - given that, from the public's point of view, wei wuxian killed jin guangshan's son and heir and then had his fierce corpse pretend to surrender so he could go kill even more people in jinlintai. none of wei wuxian's (objectively correct) arguments about ethics or how one should keep their word, in the ensuing argument after wei wuxian showed up at the nightless city pledge conference, would have held any water for the gathered audience - because, from their point of view, wei wuxian broke his word first by having wen ning pretend to turn himself in only to then kill more people.
and, after the nightless city massacre, the first siege is inevitable. there is no society in the world that, given the power to do otherwise, will allow someone who slaughtered thousands of their member to continue to exist. this remains true regardless of whether this mass-slaughterer is nobly born or not - because, at that point, the matter is no longer about preserving existing social structures, but rather survival.
after all, canon has demonstrated that MDZS society will not tolerate endless unpredictable violence from anyone, even if they are powerful and/or of high status: for everyone, regardless of status, there is a threshold of violence and unpredictability that society will not tolerate. if this was not the case, then the entire sunshot campaign would not have happened at all; qishan wen before its fall, after all, was the most powerful sect, recognized by society as a noble sect of righteous cultivation.
thus i believe that, if the second list of events had happened to someone nobly born instead of wei wuxian, then the same outcome would have occurred. if the "yiling patriarch" who killed jin zixuan, whose fierce corpse turned himself in only to kill more people, and then killed another 10-3000 people at nightless city, had been wen chao instead of wei wuxian, then the same outcome - the first siege of the burial mounds - would have occurred. even if the "yiling patriarch" had had a powerful sect backing him, the events of canon (eg. the entire sunshot campaign) indicate there is only so much violence and unpredictability the public is willing to tolerate, even from people of high status, before they respond with violence in kind.
by the time of the first siege, the people's problem with wei wuxian was no longer that he did not know his station or that he enacted violence against his betters, but rather that his behavior had, from their point of view, proven that he was unpredictable and unable to be negotiated with. people are able to tolerate violence so long as they feel that violence is predictable; so long as they can be certain that, so long as they behave in specific ways, then violence can be averted. however, how is one supposed to have this reassurance if the other party is unable to be negotiated with - if the other party freely kills peacemakers (jin zixuan), pretends to surrender only to kill more people (wen ning killing more people at jinlintai), and then kills thousands more people on top of this?
thus, it is true that, prior to the qiongqi pass massacre, classism was a major factor in what biased the public against wei wuxian. it was not the only factor, as bias against demonic cultivation and bias against the wen also played a major role in biasing people against wei wuxian. neither of these have anything to do with classism: the bias against demonic cultivation is based in the fact that wei wuxian's cultivation desecrated the dead, and the wen were nobility pre-war.
however, the public's reaction to the events of the qiongqi pass massacre and afterwards are no longer primarily motivated by classism. instead, the public's reactions are motivated by the fact that, from their point of view, wei wuxian has proven himself to be unpredictably violent and unable to be negotiated with. by this point, it was no longer wei wuxian's status as the son of a servant turning the public against him, but rather his actions. had a nobly born person done exactly as wei wuxian had done, the outcome would have been the same.