The hooves are tipped with collagenous eponychia, which prevents damage to the amnion and beyond.

America! America! God mend thine ev’ry flaw; Confirm thy soul in self control, thy liberty in law!

It was one of the worst feelings in the H-Block, one of the worst experiences to sit and listen to somebody getting beat. Because you were totally powerless, and you would always get somebody shouting at the door, “You shower of bastards!” It was always a crowd of screws and one or two naked men in a cell. They had total control.

His overt revulsion is caused by the Wincest fan fiction — the Sam-slash-Dean pairing that also alarms Dean in the epigraph of this paper — and to a Dean-slash-Castiel (or Destiel) kink meme in which Castiel has a crab claw for a hand.