What would you do if you were in my situation?

I'm really stuck on what to do about this situation with my boyfriend and his friends. I don't want to say all his business but I will just say 2 years ago he went through something awful at the hands of an old friend. A lot of his friends still stayed friends with this friend who not only caused him a lot of pain, but pled guilty to causing him a lot of pain so it's not a two sides thing. He's already confessed. I don't think my boyfriend has very good friends. I knew this person too and even before me and my boyfriend started dating when I found out what happened I avoided this person like the plague. My boyfriend doesn't want to complain because he's tired of being treated like a burden. I have told him that me not being around someone who's caused him pain isn't him being a burden. It's the right thing to do. One of his friends said some absolutely horrible shit to him. It was disgusting stuff. He literally weaponized his trauma to hurt him. Well said friend apologized and my boyfriend told me. I said "Why would you want to be friends with someone like that? He's horrible." My boyfriend goes "Babe. If I stopped being friends with everyone who treated me terribly at some point I wouldn't have friends." I feel like I should tell him that he doesn't need friends like that but I'm not trying to come off as controlling. I want to be helpful and show him he needs better friends but how do I do that without coming off as controlling?