I don't like when my boyfriend hangs out with his single friends. I think they are a bad influence and wouldn't stop him from doing something dumb if he was drunk, they would encourage him if anything. What do I do?

It seems to me the real problem would be your boyfriend getting drunk. It is his responsibility to drink in moderation and act accordingly. You should be talking to your boyfriend about that, not him hanging with his friends.  Everyone needs some friend-time and to get away from the significant other.