“When someone tries to derail an argument with an insult, your response depends on who the audience is. If the two of you are alone, say something like, “This isn’t recess. I’m out of here,” and walk away. You’re not about to persuade the jerk. But if there are bystanders, ridicule the insult. “So Bob’s answer to the problem of noise in this town is that I’m a jerk. Was that helpful to you all?” You turn sophistry into genuine banter.”
