In-group vs. out-group dynamics.
If you're apart of a group, certain things are acceptable to say or do within that group. If you don't belong to that group, it is not acceptable to say or do certain things. It isn't rocket science.
White people always make a fuss over this, but my biggest question is always if you are White, what reason would you need to say the N word? None.
I'm not your *****, I don't pick your cotton. Slavery ended.
