Power at a lunch table shifts the moment someone stops laughing at the mean joke.

Mean humour runs on consent, and the laughing is the consent. One person not joining in changes the arithmetic immediately, because the joke needs a room and the room has gone uneven. Nobody has to make a speech for that to happen. Who sets the tone at a table gets decided by whoever withholds the reaction.

You do not have to confront anybody this week. Keep your face still the next time the joke is at somebody’s expense, and change the subject if you can. If the person being laughed at is nearby, say something ordinary to them afterwards.