Letterman should have taken a page from the late, great, Andy Kaufman's book (coincidentally, Kaufman's apology was on the show, itself.)
Andy was never afraid to be a man and apologise for something that was crap (or, for that matter, he was never afraid to dish out the crap, either.)
http://www.youtube.com/watch?v=EkKhuP3-j6E :lol: