There's a lot of good advice here. Thank you.
The thing is, I get pretty rattled when he says mean things. He acts like her disability is catching. It's easier for me to consider the more violent suggestions because they mirror my real feelings, even though I know everyone's joking.
I need to reread some of the above replies and try to work on keeping calm and behaving maturely. Unfortunately, when it comes to defending my pets, I'm not very good at that. I still hold a grudge toward an old lady who made fun of my poodle's name once (it was Irving, and he was a wonderful, wonderful boy).