What should I do?... (I know this isn't really an app for this sort of thing, and I don't know which group to pick, but I need advice)

Okay, so my boyfriend has been sending off the wrong signals to my family recently. I've told him before that he needs to kind of bite his tongue around my family because they tend to overreact. I am happy with him, but he can be a really big asshole at times too. Yesterday, him and I got into a fight because he pissed off my sister's boyfriend by making a highly unnecessary and uncalled for comment. I reminded him to bite his tongue and told him to tone it down. Then he started going off calling my sister a bitch and her boyfriend a lazy dick. And it started a huge fight, in which he claimed that I was talking shit about his family. Truthfully, I don't know if I can be with someone who's going to be like that. But at the same time, I don't wanna lose him. So I don't know what to do....