The BF can't really apologize for what other people do and say but he can apologize for exposing his GF to it.
If they are talking about moving together when their schooling is done, it really is time to talk about the future and what his expectations are for spending time with his family. Were my family like that, I wouldn't want to expose my BF, let alone any future children, to that kind of bigotry and racism. And if the BF doesn't understand her concerns, it might be time to seriously reconsider the relationship, no matter how good a guy he is. If he's willing to expose children to open racism and bigotry, frankly, he's not that good a guy.