Laugh along every time and people assume the joke never hurt.

Laughing is the quickest way to make an uncomfortable moment pass, and it also tells everybody the joke was fine. People genuinely cannot tell from outside, so a joke that stings gets repeated because the evidence says it landed well. That leaves you managing the room at your own expense. Nobody is going to guess.

You do not need a confrontation to change this. Not laughing is enough, or saying the flat version once: I would rather you did not. Say it privately to one person if that is easier, and you will usually find the joke quietly disappears.