The moment you start name-calling, everyone watching knows you ran out of points.

The switch to insults is the clearest signal in any argument. It happens at the exact moment the reasons run out, and everyone watching registers it, including the people who agreed with you thirty seconds ago. You lose the room and the point in one move.

When you feel the insult arriving, say nothing for a second and ask a question instead. If you have genuinely run out of reasons, saying so is stronger than the alternative.