Cruel jokes get a laugh from the room and a quiet reputation from everyone in it.

The laugh is loud and immediate, and it hides what is actually happening. Everyone in that room is also updating a private file on you: this person will trade somebody else’s comfort for attention. Nothing changes on the surface, and then months later you notice certain people never tell you anything real.

If the joke only works because somebody is the target, it is not the only joke available. Being funny about a situation instead of a person keeps the laugh and drops the cost. Try it once and notice that nothing is lost.