I've found that this works well with people who consistently try to make other people look and feel foolish. Spectators will only notice the loud person and not the other one, and it turns the tables on the jerk. Here's a bit of sample dialog to illustrate:
John: Lisa is so much prettier, smarter, and more talented than other women.
Felica: Hmm? I didn't catch that.
John (a bit slower): I said, Lisa is so much prettier, smarter, and more talented than other women.
Felica: I'm sorry, John, I think this wind is drowning you out. Could you please repeat that?
John (loud and very slow): I SAID, LISA IS SO MUCH PRETTIER, SMARTER, AND MORE TALENTED THAN OTHER WOMEN.
Felica: Gosh this is embarrassing, but I just can't understand what you're saying. Could you say that just one more time?
At this point, he'll either have to shut up or everyone around will be staring at him. It's easier to do it than it is to explain it, so you'll need to actually do this to see how effective it is. You might also try answering as though he just said something about the weather or his bunions. Add a tolerant, sympathetic smile to finish.