They tried to drag you into the mud. Staying clean is the whole flex.

Some conflicts are designed to pull you down to a level where the other person has more practice. Refusing to go is not about being above anybody. It is recognising that a fight on those terms has no winner, and that you are being invited to lose slowly. Staying out of it leaves the mess where it came from.

When someone escalates, keep your own register instead of matching theirs. Say the boring true thing rather than the sharp one. Anyone watching will draw their own conclusions without help from you.