According to Merriam Webster’s learner’s dictionary (and everyone else in this country besides Todd Palin) “knocked-up” means PREGNANT not RAPED:
knock up [phrasal verb]
1 knock (someone) up or knock up (someone) informal a chiefly US impolite : to make (someone) pregnant ▪ She got knocked up. [=she got pregnant] b Brit : to wake (someone) by knocking on a door ▪ knocked him up at 6 a.m.
Just in case ol’ Todd is reading this the definition of rape is:
1 : an act or instance of robbing or despoiling or carrying away a person by force
2 : unlawful sexual activity and usually sexual intercourse carried out forcibly or under threat of injury against the will usually of a female or with a person who is beneath a certain age or incapable of valid consent — compare sexual assault, statutory rape
3 : an outrageous violation
So when David Letterman said that Sarah Palin’s daughter got knocked up by Alex Rodriguez, it was a bad joke. It wasn’t even funny. At all. But he did not say that anyone should rape anyone. In fact, rape was never even insinuated (unless you really want to stretch the statutory rape issue–which I don’t).
As far as the Eliot Spitzer remark, that was a slam against Eliot Spitzer not Sarah Palin or her daughter.
Then there ‘s the remark about Sarah Palin going to Bloomingdale’s to buy more make-up to “update her slutty flight attendant look”. Well, now, that one was just funny.