Rain Man is Dustin Hoffman humping one note on the piano for two hours and eleven minutes. It's his dream role. As the autistic savant Raymond Babbit, he's impenetrable: he doesn't make eye contact or touch anyone or carry on a conversation; he doesn't care what anybody thinks of him. Autistic means self-involved, and Raymond is withdrawn in his world of obsessive rituals. So Hoffman doesn't have to play off anybody; he gets to act by himself.
Ouch. It's great to see such a huge insult written so well. Kael's use of punctuation is so intricate it's like watching a great magician: you see just what she wants you to see, the mechanics are invisible. Also, word choice. The word "humping" elevates this from disposable to classic.