The worst-tempered people I've ever met were people who knew they were wrong.

Mizner’s line suggests that anger and irritability often mask insecurity rather than strength. People who “know they are wrong” may become defensive because admitting error threatens their self-image, status, or control of a situation. The “worst-tempered” response is thus a psychological reflex: hostility substitutes for humility. The epigram also implies a social lesson—when someone reacts with disproportionate temper, it may signal that the argument has reached a point where facts are against them. As with much of Mizner’s humor, the wit lies in reversing expectations: certainty of being right is not what makes people furious; the private recognition of being wrong does.