Obviously, we should all avoid bad words at all costs. I've always said that if you really want to curse, it's okay as long as it's in front of other people who don't mind hearing bad words. I think that bad words can also be acceptable in very specific situations when you want to make a point. All of my friends know that I can't stand cursing, so they know that if I do say an objectionable word, they know I'm really angry or trying to underscore something. When you don't ever use bad words and you suddenly use one, people will understand that you're trying to make a point.
I'm not trying to condone using bad words while you're angry or anything like that, but I think it's just an interesting point to note.