Two Great Writers who became misanthropes

The first is Jonathan Swift, author of the popular "Gulliver's Travels" & the critically acclaimed & erudite "Tale of a Tub" on the schisms present among the three branches of Christians, Catholic, Protestant & Calvinist. With brilliant parody, he writes how all three moved away from the simple teaching of the Gospels. But in the fourth section of Gulliver, he depicts a noble race of horses using an abominable race of humans as slaves. Such was Gulliver's repugnance of "Yahoos", as these humanoids were called,  that after returning home, he could not abide his own family & lived among horses in his stables. In real life, Swift suffered from senile dementia which turned into terminal dementia.

The second was the great American, Mark Twain, who gave us the immortal "Tom Sawyer" & the even greater "Huckleberry Finn." Even though he suffered from depression, he was apparently in his right mind & wanted his unfinished writings destroyed. But they were published posthumously as "Letters from the Earth" with chapter headings like "The Damned Human Race", "Was the world made for man?", "In the animals' court", "The Lowest Animal" etc., which make his ideas evident.