"Nine times out of ten, an argument ends with each of the contestants more firmly convinced than ever that he is absolutely right." The scoreboard is rigged: "You can't win an argument. You can't because if you lose it, you lose it; and if you win it, you lose it." Winning costs you the person's goodwill — which was the actual prize — and the loser "will resent your triumph." The corollary is absolute: "never say 'You're wrong'" — even to a customer, even when you're right. The replacement move is respect for the other opinion and an instant, honest admission when you err.

— In our words · Source: How to Win Friends and Influence People (Dale Carnegie)