> It's an incitement to violence
No, it's not. Otherwise, wouldn't that imply we should outlaw being mean altogether? Is being mean always an incitement for violence? Yes/No? I think it's clear, it's not.
> it's horrifically bad for the mental health
Citation needed.
> as a form of discrimination against those people
Again, no. Discrimination requires that it be 'unjust or prejudicial treatment', hate speech does not. Hate speech could be as little as explaining factual reasons you don't like another race.