and right-wingers on the internet have been defending him, naturally.
It's nothing new, there was the referral to the pubescent Chelsea Clinton as "the Whitehouse Dog" back in the day, and it's really something that he has to do. Limbaugh speaks for an audience who imagine everyone to be as malevolent as themselves, who believe that the urge to bully is a basic and universal human instinct, that decency is maintained only through the force of 'or else', so that any kindness or courtesy which isn't inspired by the basest tribal loyalty must necessarily by inspired by fear.
Limbaugh has to attack the president's children in order to show that he ISN'T AFRAID TO GO THERE. And it goes without saying that every single one of the millions of Democratic voters are personally responsible for every crude joke that somebody made about Trig Palin, so that we have no right to complain about Limbaugh, lest we be hypocrites. And of course there's the old 'what about all those things you libs said about Bush? What happened to free speech' saw.
So when they make crude attacks on the president's family we can either except that we have no right but to sit there and take their holy vengeance, or we can complain and so let them know that we are bothered by their actions. Either way right-wingers will be able to maintain the illusion of having liberals under their heel that they constantly need to have, and never mind about hurting the feelings of children. If children aren't fair game, than why are they smaller than us?