It's very common for a word to be OK for in-groups to use and not OK for out-groups to use. When someone in the in-group uses it, it's acceptable because they identify with it and it's a term of endearment. When the out-group uses it it's a label and a slur.

I'm not going to list any of these because I'm not in most of the in-groups (other than nerd) but if you think about it I'm sure you'll be able to come up with some examples.