I see it as just a way of translating the vague idea of "honorable behavior" into mechanics. I'm fine with that as many people expect honorable behavior from knights, even if historical knights were not paragons of honor. I believe the knight's other mechanical advantages do compensate for this mechanical disadvantage, and the net result is a fairly well-balanced class. The knight would appeal to players who want a character that does not need to take advantage of an opponent's distraction or lack of preparation to beat him.