The argument people are using is that Snape shouldn't be black because Harry will be racist for suspecting him of a crime.

I'm trying to understand the psychology of the people making this type of argument.

Are they simply racist and lying about why Snape can't be black?

Did they interpret Harry's dislike and suspicion of Snape as being for literally no reason, so now if he's black that will be the reason? Pretty sure Harry disliked and suspected Snape because of Snape's actions. Snape is an abusive prick. Maybe they've only seen the film, which shows less of Snape's asshole behaviour than the book did.but the film also showed that Harry suspected Snape because of evidence, like Snape being bitten by Fluffy made it seem like he tried to sneak past him.

Are these people so simple minded that if there are clear reasons Harry dislikes Snape, they won't see it if Snape is black?

Is it because they themselves hate black people, they can't comprehend the difference between hating a black person and hating them BECAUSE they're black? Is there no distinction between these concepts in their minds? If they hate a black person for legitimate reasons, they also hate them for being black?

Is it that these people got called racist for calling a bad black person a racial slur? If a black person is being an asshole, you can call them an asshole, but if you call them a racial slur, I will think you're racist. Perhaps these idiots call black people they dislike slurs and don't understand why they're called racist for it, so they think anyone who hates a black person, even if it's for good reason, will be viewed as racist.

Perhaps they assume the writing of the show will be different because Snape is black. They think it automatically means the show will try to make it part of an anti-racist message. They think the actual script will call Harry racist and make him learn a lesson about suspecting black people of crimes.

I've seen it claimed that the complexity of Snape's character will be ruined because now they hatred towards him from other characters will solely be about race. So regardless of Snape's actions, if he's black then that will be the only possible reason people dislike him?

I've seen it claimed Neville will look racist now for fearing Snape. Do they think the show won't show Snape bullying Neville?