There are certain words that can only be used by you if they describe you. If they don't describe you, then their use is considered
inappropriate,
politically incorrect or downright
offensive.
Usually they are used to describe social groups of one kind or another. For example, if a suit calls a geek a geek, then this is considered offensive. But if a geek calls a geek a geek, then this is considered to be not only polite, but almost a term of endearment.
There are many words like this, including: nigger, geek, nerd, wog, chink.