Ever been in an argument that starts getting really nasty really quick? Self-improvement site Pick the Brain suggests that you put a stop to it:
Firmly but calmly state: "You're very angry right now and you're saying things you don't mean (give them the benefit of the doubt). I'm going to excuse myself. We can talk again after you calm down." Then leave the room or ask them to leave.
Not only does this give the hothead time to cool down and reconsider his/her choice of words, it also saves you from retorting with words you probably will regret.