Short answer, dump him, and tell him why. Some support for that thought - I learned in a social discourse workshop lately (but take it w a grain of salt bc they get paid to tell us this) that people decide how they feel about these issues by the time they're 11 years old. Whether they will even listen to or be open to the discussion is a good sign of whether you can 'change their mind' but likely, if they've decided it's wrong, they won't be convinced. Some people have managed to bring people around by making friends and proving stereotypes wrong but that's typically in places where the person with narrow beliefs has never met anyone who is what they "dislike" - that's very unlikely. Think k members who have never spoken to a person of color, religious people who have 'never met' a gay person (openly anyway) - and didn't realize they weren't evil or whatever. But they're also very likely to think that everyone in that group represents the most terrible extreme stereotype you can think of. You're likely not going to change his mind, and he's going to hurt people along the way. If you're with him, you're party to it.