I gave this some thought when I got neg repped for violating the Third Commandment. I concluded that there was nothing to do about it.
It seems to me that the general custom and practice on IE is to reserve neg reps for really objectionable posts rising to the level of serious disruptions or blatant fabrications. IMO cursing does not meet that standard.
But I think a poster should be able to neg rep whatever and whoever he wants. The neg-repped poster can then respond in kind (although that would be stooping to his level), call out the neg-repper publicly for giving a neg-rep under circumstances that puts him outside the bounds of our general custom and practice, or, to the extent the neg-repping reaches the level of an all-out assault on the cursing poster's reputation level, i.e. the level of harassment, involve a mod.
But as long as I'm just receiving an isolated neg rep here or there, I don't really care. Freedom of speech and all that. I have the right to curse and he has the right to express displeasure. I may find his mode of expressing displeasure offensive, but freedom of speech means "protecting the thought that we hate."