Most Helpful Girl
I think lip rings are really sexy on guys. However, when my partner told me he wanted to get one, I felt really apprehensive about it. I was used to him looking a certain way, so I wasn't sure how I'd feel about it if he changed his appearance. I felt the same way when he decided he wanted to grow a beard, and when he decided he wanted to grow his hair long. I'm attracted to him the way he is, so I'm kind of resistant to him changing his appearance.
That said, I'd never get mad at him for wanting to do these things and I'd never tell him he can't. It's his body, so its his right to do whatever he wants. Even if he wanted to get a face tattoo---I'd probably give him some arguments for why I don't think its a good idea and gently tell him that I'd find it unattractive if he did so, it would still be 100% his decision.
Your boyfriend sounds immature and controlling. He sounds like the type of guy who has the "sluts are okay to f***, but not to date" view of women, which is pretty deplorable. Also, if my partner called me a slut, even once, he'd be out the f***ing door. I wouldn't tolerate it. I mean, maybe I could understand calling your girlfriend a slut if she cheated on you, but over something as benign as a navel piercing? WTF. Getting a piercing does not make someone "slutty".1