Just because you've seen other comics (like, say, Lisa Lampanelli) insult their audience doesn't mean you should—at least, not yet. And it may be tempting, particularly if you're feeling strapped for material or if someone is heckling you. Of course, you should respond in that instance, but watch how far you take it. It can be easy to alienate your audience, and you always want them on your side. Plus, you never know if an audience member is going to take a joke the wrong way; many a comic has a story about someone from the audience waiting for them after the show. If they feel humiliated and have been drinking (which, given the nature of the comedy club, is likely), you may be bringing trouble on yourself.