What's so bad about these messages between my boyfriend and i?

Probably because you and your boyfriend are talking about ual things and he is using bad language. I personally would be more mad at the boyfriend, since you seem to be trying to mellow him out. It may be that your father just doesn't want to think of you as a grown-up. Or he agrees with your boyfriend about Ryan and is grounding you to keep you away from him and his prom.