Not laughing at the cruel joke is a small rebellion. Keep being a rebel.
RESILIENCE
RESILIENCE
A joke at somebody’s expense needs the laugh in order to work. Without it the room goes slightly quiet, and whoever made it notices, which is why not laughing is never a neutral act. You do not have to make a speech about it. Withholding the thing the joke was fishing for is already the objection.
It costs a second of awkwardness and it is a choice every single time, not a personality you either have or do not. Let your face do nothing and change the subject. If there was a target, find them later and say the ordinary thing.
When did you laugh at something you did not find funny?
Free, with nothing to buy inside it.