Refusing to laugh at the cruel joke is a small, brave kind of faith. Silence can be a stand.

Cruelty in a group depends on the laugh. It needs the room to supply approval, and anybody who withholds it removes a piece of the support. You do not have to object, make a speech, or get into an argument about it. Not laughing is visible, and the person telling the joke notices immediately.

Keep your face still the next time it happens, and change the subject. If you can manage it, say something ordinary to whoever the joke was about afterwards. A room often follows whoever did not join in.