Honestly, in my opinion its valid to dislike someone for any reason. Disliking someone is just an opinion, what matters is how you actually treat someone.

Its totally okay to make a generalized assessment about someone because of the ideas and philosophies they espouse, such as being an anti. Just as long as you don’t treat them in a nasty or abusive way just because of their opinions, and try to be willing to revise your opinion of them if they turn out to be different than you expected.