The argument I've heard to counter this is the idea that economic markets are efficient even when many participants are irrational because the irrational participants cancel each other out, amounting to random noise.

A market can find efficiency even when there are a significant number of irrational participants because the rational minority are in agreement, and the irrational minority step on each other's toes.

Similarly, if 44% of a democracy has an irrational preference to always vote for Team Blue, and 44% of a democracy has an irrational preference to always votes for Team Red, then the remaining 12% actually decide which team wins.