It doesn't matter if they use it among themselves or not. It takes on a different meaning when a non-black person uses the words, regardless of their intent.
Ever hear people say, "Don't tell dirty jokes in strange company?" It may be a funny joke between you and another person, but someone within earshot is bound to take offense.
Without going off on another topic here, all you need to remember is this: The word was derived by people that had one intention - dehumanize blacks in the latter 19th century. Although I agree they should not use it between themselves, that word is off limits to you and me and other non-blacks. And all these white adolescents using the word today are scary. I would, however, put it on their shoulders to kill the word. It confuses people when they see blacks using it between themselves, so I guess the time has come for finger-pointing.