You don’t have to be a hero. Just be the one voice that says “that’s not funny” when it isn’t.

The bar for stepping in is much lower than people imagine. Nobody needs a speech or a confrontation, because what keeps a room going is the appearance of agreement, and silence gets counted as a vote. One flat sentence breaks that, since it proves the consensus was never real and hands everybody else permission. It usually costs less than you expect, though not always, and reading the room is fair.

Have four words ready for the moment: that is not funny. Then change the subject and carry on. You are not rescuing anybody, only declining to be part of it.