The Houyhnhnms cause Gulliver to hate himself.
Step-by-step explanation:
He compares himself to the human-like but beastly Yahoos, who are held in subjection by the Houyhnhnms, and learns to hate men for not being horses. Here, Swift's satire is double-edged; the cold Houyhnhnms are imperfect, just as the Yahoos are. Gulliver is disabled by his self-hate; he becomes too critical and isolated to love even his own family.