The problems here go a lot deeper than what you’re seeing. Just looking at this I can already tell the guy has probably had folks approach him when you’re not looking, and then suddenly make arguments and disagreements for everything or been shitty about whether those agreements are IC or OOC. They probably had a lot looser rules in the past! But people misused them as jumping off points, found loopholes, and began ruining their RPs by forcing in disagreements when they just wanted a relaxing time out. They might even have trouble coming up with responses, or simply do not want to deal with it here, in a space they created to get away from all the other trouble. Maybe some jackoff couldn’t tell the difference between an IC or OOC argument, and kept making arguments as a mun that his character couldn’t fight against, and it drove him up a tree! He finally snapped. A rule is placed.

Now, since someone has clearly been such an idiot and an asshole they have to sit there and go through every single disagreement beforehand to make sure they can handle it, and understand it, because misunderstandings happened so often they started losing partners, or may have even had someone spreading gossip about them, or been mean about this stuff. They’ve likely just given up. At a certain point, they’ve decided ‘I don’t want to RP this anymore so much I’m just going to nip it in the bud’ and everyone else has to deal with the fallout. They now have to comb over everything. They have to make sure that bad shit doesn’t happen again. Believe me, there’s a major likelihood there’s a list of players out there to blame for conditioning someone to fear and dislike disagreements, before you get on this guy’s case.

The other option being of course, he’s tone deaf to arguments. He may not have the actual ability to see an argument, or understand how intense the other player is being. All he knows is every time someone has an argument, he misses it, and they get mad. What’s the best way to save face on that? You ask for warnings. What does everyone else think about him adapting to an issue? “He’s ridiculous.” It sucks to be on either side of this.

Now, the problem is fixing it. Does he want to fix it? If not, just leave his rules in peace. If you approach him for RP, you’re bound to his rules. (Give or take your morality spectrum. Don’t do things that hurt you. Step out of RPs you aren’t comfortable with regardless of rules against that. Exits cannot be rulebound. You can leave for any reason you like.) He might get used to it later, or feel better about it when his rules are followed. If you show respect, he can grow as a person. He can adapt, or learn to see arguments coming. He can get over whatever people have done by healing from it. This is his choice of method to heal. This is his choice. This is his RP, and his character, and his rules. You do not have the right to change it by force. That is entitlement, and you do not get to have entitlement for another person’s play time.

As time passes, if you don’t get irritated with having to mention ((oh my character will disagree with that)) occasionally, they might make allowances. The more small and petty things that come up often. They will grow to trust you, in particular, given that you follow the rules. The thinking is simple: If you can follow a suffocating over the top rule, not only do you actually want to RP with them, but you can be trusted not to be here explicitly to cause them trouble. You can be trusted. You earned the trust by doing something extreme of your own volition. Don’t do it if you don’t think you can handle it. It’s not your beeswax to melt.

At the same time this is a new rule, and I’m not entirely sure they know what they’re in for. This is gonna make things hella more complex and obnoxious and over the top for them. They’re gonna have to deal with waaaay more shit in this particular instance than they probably want to. The fallout and blowback from this is gonna be hella just in terms of how many posts will have the flow interrupted or postponed by an additional pair of responses before a real response. In chat RP, easier, in forum RP like Tumblr? Hahaha, wow what a wait. You, in particular, have a very unique situation here. You already have a door opened with them from the past, and the rules changed while you were there. While the advice so far has been about approaching someone with a weird old rule, this timing thing changes stuff. You got a foot in the door. 

Politely ask, “Does this new rule apply to our RPs? Have we had some issue in RP that caused this? Because if so, I’d like to fix it.” Then, likely, he’ll explain. The rule does apply to you, or it doesn’t, or it does much lighter than you’ve kind of expressed here which sounds downright draconian. He’ll tell you what caused it, if you nudge, and you can get a better picture. An understanding. He might already have trust built with you and will make an exception for you. He might be doing it to scare off some annoying kids, but you’re cool, sorry. If not, well, you’ve fucked up somehow and now you get to play in that argument pool trying to fix what you’re doing, or obeying his rules, until he’s satisfied. The other outcome is no one plays with him. Theoretically, no one ends up being able to follow this ideal he has. He never loosens up. He’s doing it out of a power play, and he’s the asshole who makes other people have rules against OOC and Pre-Planning. I mean I’m gonna fight for victim rights all the way to your grave, but if it really is just some jerk off seeing how bad he can make his rules and still get RP as some kinda social experiment? People will stop playing. Word will get around he’s an unreasonable turd. When he comes to you bitching he never gets RP anymore, or when he starts making posts to that effect. THEN you can approach him. “Well, your rules are a little harsh, that disagreement one is a doozy.” Talk rationally no matter how they react. Do not give in to emotional yelling or the like while talking, and give them space.  If you’re in an argument and your opposition sits there reaming you with point after point do you finally give in because they’re so smart? Or do you fuckin’ sulk, have no time to realign your ideals with what makes sense, and argue back regardless of what they’re saying because you feel unheard, embarrassed, and like they don’t understand you? If you can do the first one, and not the second in any way shape or form, I’m quite frankly completely surprised. Keep this in mind, if you move slow, and let them deal with each point, and talk about their side of things, and admit they have good points (if you can find any) they are a hell of a lot more likely to think of you as a friend, and not an enemy to defeat. Slow exchange of ideas gives them time to work through whatever they have against the idea, or gives them time to fully understand it. Slow argue, patiently, one thought at a time. Discuss, don’t smother, belittle, and condescend even accidentally. Those are the three most likely outcomes. Finding out more details about why something happened will greatly inform you about how to approach it. People don’t just do random bullshit, they typically have reasoning behind it. Even the weird shit. Paste on your best friendly smile, write kindly, and try to understand them even if you personally don’t think it’s their best option. Work with them to try and figure out a better solution to whatever is buzzing around hurting them. You might be surprised to find out what’s going on. In all cases, that is a hell of a rule, and they’ve just taken on a massive burden which makes them look unappealing to other RPers, regardless of how safe it makes them feel. Shit is not likely to go right if they want more RP, or they can’t handle the load. Be gentle. Be loving. Be excellent to them. Learn, talk, communicate, and grow.