No one can step into another person's mind and know for sure the "intent" of anything. In this case the perception that he told a joke about the daughter who was at the game is also the reality of the situation.
If I told a rape joke about one of President Obama's daughters, but in my mind I was thinking "Hillary" it wouldn't matter to anyone. It would be offensive.
Letterman did the right thing to try to apologize. It's too little - too late ... but time will tell if he means it. In his favor I don't remember him telling rape jokes about children before - but then again he doesn't see conservatives as the equals of liberals - or our children.
Does anyone remember him calling a liberal governor "slutty"? I'd like to know - but I already know - his contempt is saved for traditional conservative Americans.
Screw him, keep the pressure on the advertisers, it’s working.