Ok, it probably makes me a horrible person, but I sometimes find the phrase, "Well, if that's what you need to tell yourself..." to be handy from time to time. When absolutely nothing else gets through to someone. And then tune out their response, whatever it is.
Jerk: You must be anorexic!
Me: Well, if that's what you need to tell yourself...
Jerk: Lisa can do everything much better than you!
Me: Well, if that's what you need to tell yourself...
But really, what's so vital about these monthly meetings? Can you arrange to see the other (nice) guests separately? Can you just not go? Can you join a different group/organization/club? I have to admit, I sometimes turn down invitation when I know a certain couple is going to be invited. I'll attend other events with the rest of the guests, but wild horses couldn't drag me to an evening when that couple is going to be there. Because I know they'll be rude and snide and make accusations and insults, no matter what I do or don't say, no matter what I do. There's no winning with some people and those are the people you shouldn't have to have any contact with whatsoever. There are always ways to work around it somehow, and it's worth looking into what they are.
Also, is there any reason DH can't stay at your side for the entire night? And if the jerk starts up again, DH can coldly cut him off with "Do not speak that way about my wife. For any reason."