Yeah, not great. I think if you understand the difference between what is a disparaging kind of 'joke' and something thats actually humorous, then you can just judge this.
"Fucking cringe." And just walk away. Don't accept any 'explanation' of why it's funny. Let them become upset by your reaction, if necessary. "Nah, we're not going to be making fun of disabled people. You're on your own."