The Christian Science Monitor has this to say:
It’s one thing to irritate your opponent. It’s another to irritate a newsperson. But when you irritate the guy who’s made a living out of making people laugh for more than 26 years, any criticism may pack more of a punch.
Don’t misunderestimate David Letterman. Letterman’s been on the air since 1982. While his show has always been a ratings success, numerous wannabees crashed and burned, badly. Magic Johnson’s "The Magic Hour" and "The Chevy Chase show" are just two examples of heinous late night Hindenburgs. It’s a tough gig.
So when John McCain cancelled on Letterman - at the last minute - you could hardly expect that the comic would take it easy on him. He didn’t.