There's a tendency in fandom to try and break gender stereotypes by feminising men but often times it ends up going so far left it goes right. There suddenly has to be a "man" in the relationship who is strong and level headed and the embodiment of masculinity. While there has to be a "woman" who is dainty and fragile and needs protection despite the ship being mlm. Yes it's fiction do whatever but when it's at the detriment of a characters characterization to the point of becoming the dominating fanon, then I just can't stand it. I also am not critiquing bl as a genre here because that's a whole other beast. Those are the only versions of those characters. I'm specifically referring to shonen slash ships. And more specifically sanegiyuu.
Giyuu is oftentimes shown as weak or portrayed as a stereotypical omega, or worst of all, as a helpless victim of Sanemi, Shinobu, and Obanai's bullying. He has no agency and is often reduced to a damsel in distress role in fics due to his perceived femininity. These roles are forced on him because he's physically smaller than the people's he's most shipped with (e.g. Sanemi) or his silent demeanor is seen as more submissive in comparison to the other characters' louder/'maler' personalities. But it's not a role that makes sense for him because if it weren't for his size, Giyuu would represent the stereotypical ideals of the silent and brooding top, especially in comparison to Sanemi. He's closed off, level-headed, incredibly skilled at his job, has a voracious appetite, and possesses an incredibly protective nature when it comes to the people he cares about, such as Tanjiro.
Narratively wise, the guilt he carries for being responsible for Sabito's death and his own lack of autonomy over his life means being a feminised bottom would probably be his worst hell. As someone who was continously protected by his sister, Sabito (even Urokodaki in the case of Tanjiro), he feels his life is governed and extended not by his own actions but by the sacrifices of those around him. He is someone who desires control over his life and being allowed to have that control as a top would offer him both the safe space and the catharsis he needs. Being penetrator is something that is so deeply personal because it is an invasive act. It requires a level of trust that Giyuu would be able to give up but would only reaffirm his fears that he's someone who needs to be 'taken care of' rather than someone who could be that for someone else.
For Sanemi, who spent his whole childhood being the protector. First, his family is against his father. Then, his siblings were against his mother. Then others would have been victims of the demons he spends the next several years fighting till sunrise. This all built up a saviour complex that came at the cost of his own body in the most blatant act of self-harm and low self-worth poorly disguised as anger. Anger, which being in the position of a hard dom top, would only be allowed to fester. Having that ability to release, to actually let someone in, and allow himself to be taken care of is what would suit him best, which are things that are often awarded to the bottom in fanfics. The vulnerability that is gained from letting someone inside your body both physically and mentally would directly rival the poor emotional regulation he's struggled with since childhood.
I also feel part of the problem is people only being able to view anger as a 'masculine' emotion. But the truth behind Sanemi's anger is that he's a very emotional person through and through. Vowing to follow his mother to hell, having poor emotional regulation and subsequently trying to blind his only remaining family member, feeding stray dogs and raising dung beetles, the self harm (of which this isn't necessarily a feminine trait but often internal suffering to the point of externally harming one self is often reserved for bottoms and subs in fics). Even Gyomei says it himself that Sanemi gets easily embarrassed, and it's due to the fact that he is an incredibly sensitive person. He's also deeply angry but it's clear still from his calm interactions with Kanae and the master that being angry is the only way he can prevent himself from confronting his feelings of inferiority for 1 being a murderer (in his eyes), 2 failing to protect his family, 3 having to fight tooth and nail for his spot as a hashira, and 4 his fear of being mocked which I went more into depth here.
Compared to Giyuu's more overtly cool and brooding character, Sanemi's character is more emotionally charged, and yet because Sanemi is bigger and stronger and angrier and scarier looking due to his scars, he is seen as a masculine character. But because Giyuu is the typical ikemen character type, without possession of the more overt traits stupidly associated with masculinity, he's reduced to a fragile baby who can't swim, can't cook, can't stand up for himself, needs to be saved. And yet the manga disproved every single one of these fanon tropes.
Even if we go by physical attributes alone, the two of them fall comically so into typical female/male character designs we see in shonen animes. Sanemi's long lashes, his styled hair that swoops fashionably over his forehead, the soft design of his face (when he isn't looking murderously insane), and most importantly, his uniform. The only other person to get the same uniform treatment that Mitsuri does in the anime is Sanemi, and yet only one of them is seen as 'gooner bait'. Mitsuri is the most feminine and femme character within the series and her and Sanemi's uniforms are the samr in different fonts and yet even after drawing that very obvious and direct parallel between the two of them, people still fail to it. It's even funnier when you consider the fact that Sanemi chooses to walk around with his titties out 'for better fighting' (female gooner bait character excuses 101) while Mitsuri ends up with that uniform due to a shit perverted tailor. But looking at Giyuu's character, we never see him take his shirt off once (which I'll count as a sorta physical attribute because his body doesn't get open to sexualization in the same way Mitsuri or Sanemi's do). His hair keeps a very rigid messy and hasn't-been-brushed-in-weeks sort of structure, which reflects his internal suffering-in-silence character. His eyes are nowhere near as rounded as Sanemi's, especially when he's first introduced. They maintain this icy calculating kind of aura while Sanemi's take on the more feminine attribute of the extremely long eyelashes.
The thing with feminising characters is it's fun until you realize everyone is doing it to one character continuously to the point of changing their personality just because they want them to be the uke/bottom in the relationship. It erases sooo much of his character and ignores his character arc entirely.
Giyuu being feminised so often especially in comparison to Sanemi, to the point of Giyuu being well known as the fandom bicycle and yet somehow almost never being a top or in any dominating role in majority of the ships just leaves a bad taste in my mouth. Everything about him that is perceived as being feminine and inherently equated with being weak is simply misogyny and homophobia in an ugly trench coat and yes I will die on that hill.