The worst-tempered people I have ever met were those who knew that they were wrong.

Letterman’s line points to a familiar social dynamic: irritability and aggression often spike when someone privately recognizes they are in the wrong but cannot—or will not—admit it. The “worst-tempered” reaction becomes a defensive strategy, redirecting discomfort (shame, embarrassment, fear of losing status) into anger. In this reading, temper is less a stable personality trait than a symptom of cognitive dissonance: the gap between what one knows internally and what one is trying to maintain externally. As a comic observation, it also functions as a wry diagnostic of arguments and workplace conflicts—when a person’s hostility seems disproportionate, it may signal that the facts are against them.