My guess is that the N word has pretty much no historical use outside of referring to darker skinned people in as derogatory of a way as possible. The F word for gays is about the only other one, unless you've got a British pal who smokes, but just about every other slur is either so obscure that it's only heard rarely, or has other legitimate uses, so you have to apply context to figure out what the situation is. N word was almost always bad, until they decided to blunt the blade, so to speak, by adopting it as a part of their own vernacular.