Well, I must say I didn’t expect that from him.
That sounds like a legitimate apology. I hope the Palin family is helped by this.
You should have avoided making that statement. But since you did make it, I think you are being viewed as 'apologizing' for Letterman. I would agree with that. It appears you have let your past (or present) bias towards liking his "humor" cloud your judgment in this obvious attack.
My recommendation is that you apologize to your fellow FReepers and The Palin's, then exit the discussion.