Being the only one in the group chat who says “nah, that’s not cool” is lonely for a minute and respected for years.

Standing as the only objection in a room is lonely in a very specific way. The joke stalls, someone says you are taking it seriously, and for about a minute you are outside the group. That minute is the whole cost. What happens afterwards is that people quietly file you as someone who says the true thing when it is expensive, and that rating never really changes.

Say it short and without a speech. Not into that one is plenty. Nobody will back you up in the moment, and two of them will tell you privately later that they agreed.