Greta Van Susteren is correct in her analysis that Letterman 'doesn't get it'. His defenders don't get it either. While there are numerous issues that these comments bring up. The basic fact remains there are boundaries (or should be), and the children of public figures should be left alone.
Other good articles regarding Letterman's joke and pathetic apology...
Did David Letterman Get a Free Pass
Dear David Letterman
Steele Suggests Boycott of David Letterman
From my perspective Steve Chapman of the Chicago Tribune in the article Palin is Right About Letterman has it right
For that matter, it's hard to see what Bristol has done to deserve the ridicule. It's not her fault her mother is a national political figure. Dealing with her situation is hard enough without being under a media spotlight.
Instead of acting as though he's the victim of someone else's misunderstanding, as he did last night, Letterman ought to simply admit he blew it, big time, and personally apologize to the Palins and his viewers.
He also should to keep in mind that if you're going to ridicule someone's sex life, you might pick on someone your own size. And make very sure you have the right person.
Letterman Doesn't Get It