When someone starts insulting me for no good reason I like to go WAAYYY over the top in return. An F bomb every third word is generally used along with insinuations of necrophilia, bestiality, heck I'd even go downright sexist.
I just don't put up with that kind of crap and should anyone else confront me about it I calmly and politely ask "Would you rather I punched hell out of him/her?"