I’ve been thinking about this a lot, I went on a trip to the dumb side (I was scrolling down the anti Snape tag) and the way people hate Severus not only seems childish and willingly ignorant because 99% of the people are talking about fanon, they hate him because Lily rejected him a million times and he wouldn’t take no for an answer, the irony of these idiots to know nothing about canon but having the courage to brag about their ignorance but the other 1% that calls him an incel feels like a projection, they go on and on how Snape is like guys they’ve known, their hate is blown out of proportion and personal that is hard to take them seriously because again, they have 0 understanding of canon and lastly, I think how they’ve been adopting Barty and Regulus, whitewashing them into poor little boys that were forced to do evil while actively and yet again leaving Severus out of this new trend feels like someone started it and was being petty like ‘see? Even the other nazis were better than Snape’ also they love to be politically incorrect but seriously hating Severus so bad and for non canonical reasons, treating him as the devil incarnate is becoming like a case of mass hysteria because I’ve yet to see someone giving an actual argument against him, not the regurgitation of the same five, six reasons
Golden Trio fans usually hate Severus for being an asshole to the kids (which is fair), while a lot of Voldemort fans hate him basically for being a traitor (also fair, because for them, he was). But Marauders stans don’t actually have any coherent reason. The only thing that really bothers them about Severus is that he was the actual victim of that little gang, and because of him, their favorites are exposed for what they were: a bunch of aggressive, privileged bullies.
Severus is also a problem because he gets in the way of turning Lily into some untouchable saint. If you really look at her choices and priorities, they come off as deeply insensitive and lacking in empathy, considering she ended up marrying a guy she’d seen abuse people for years. And as for James, he’s left looking like a privileged, abusive jerk. And they don’t like that, because for some reason they’ve convinced themselves Lily and James were flawless heroes who should basically be canonized when in reality, they were a hyper-normative, privileged couple who never actually knew what it meant to suffer, and who ended up dead because they thought playing at resistance was a game and because of their own prejudice against the people around them.
Basically, they’ve got nothing in canon to back their headcanons up, because canon makes their faves look like victim-blaming, abuse-excusing, classist assholes. So all they have left is to make up whatever crap they can.