Why does Lemuel Gulliver struggle to live among people after returning from the land of the Houyhnhnms?

After returning from the land of the Houyhnhnms, Lemuel Gulliver struggles to reintegrate into human society because he has become profoundly disgusted by his fellow humans, whom he identifies as being essentially the same as the brutish, filthy, and greedy Yahoos.123

During his time with the Houyhnhnms—a race of rational, virtuous, and benevolent horses—Gulliver develops a deep admiration for their way of life, which is entirely devoid of deception or evil. In contrast, he comes to view humanity as incapable of achieving such rationality and virtue. This experience leaves him so alienated that he avoids his own family and prefers the company of horses, with whom he converses instead of people.123

Ultimately, this behavior suggests that Gulliver himself has become imbalanced; his proud identification with the Houyhnhnms and his intense disdain for mankind reflect a misanthropic shift, illustrating the satirical point that humans often fail to live up to the ideals of reason they claim to possess.123