My main point is that using profanity violates all of the rules of persuasion.
When someone calls another a profane pejorative, I seriously doubt that he’s interested in persuasion.
Unfortunately, in certain social groups, profanity is part of their standard vocabulary, about as meaningful, as “uhh”, or “well”. If one is trying to make a point and avoids using these words, the listeners may comment that the person is trying to be better than them. As such, he has been less effective at persuasion. So, in those situations, profanity wouldn’t violate the rules of persuasion.