As everyone knows by now, David Letterman finally apologized to Sarah Palin and her daughters.

It was too late. We’ve seen the ethical essence of David Letterman, and there’s nothing funny about it.

Comedians are supposed to say amusing things, and whether their comedy is in good taste or bad, appropriate or inappropriate, benign of offensive, is usually a judgement call. Jokes that appeal to an audience’s baser instincts, such as sexism, racism or just meanness, may cast doubts on the character of both the joke’s transmitter and receiver, but funny is still the key word. Comic Wanda Sykes, who got President Obama to chuckle when she wished kidney failure on Rush Limbaugh at the Washington press corps dinner, would have received less criticism had she actually said something funny or clever enough to compensate for her cruel tone.

There are jokes, however, that may cause actual harm because of their setting or the identity of the joke-teller. A joke that may be hilarious and harmless at a private party could be disastrous on national television, and while a Jay Leno gag about the Special Olympics might be easy to shake off as momentary bad taste, when President Obama uses the competition in a quip (as he did to make fun of his own bowling skills), it was a regrettable gaffe. Sensitive and innocent people were hurt.

The culture has evolved some fairly straightforward ethical rules about jokes in the national media. Public figures are fair game. Private citizens who have made the news by doing something illegal, crude, unusually stupid or strange are also legitimate targets. Clearly taboo: making jokes about non-public figures only because of their age, gender, sex, disability or race, and ridiculing children, the disabled and others who are unusually vulnerable or unable to defend themselves.

Letterman has made many fairly crude and mean-spirited jokes about Governor Palin, though he is not the only one. It is clear that Letterman believes his ideological differences with the Alaska Governor justify especially nasty treatment. In this he is usually on safe turf, given his audience and the current tilt of the national media, though Letterman dishonestly persists in claiming that he is an “equal opportunity offender,” in the words of Don Imus, another wit who has different standards for those he likes and those he doesn’t.

Dave’s Palin-bashing finally appeared to cross the line with his joke about the governor’s trip to Yankee stadium and his quip about her daughter getting “knocked up by Alex Rodriguez during the seventh inning stretch.” Palin’s 14 year-old daughter was her companion at the game, so Letterman’s joke had the effect of suggesting that the statutory rape of a child was amusing. Palin appropriately called Letterman on it.

[At this point, permit me an aside about women’s groups and media watchdogs. When Don Imus, in some spontaneous banter on his radio program, suggested that the young women who played on a college basketball team were “ho’s,” women’s rights groups ran him off the air. These weren’t public figures, they said, but young women who were attacked, out of the blue, for their gender and race. Imus immediately apologized, but to no avail. He had few defenders, in the media or elsewhere. But when Letterman made his joke that, regardless of his intent, had the effect of making attributing public sexual activity to a 14-year old girl—-at least Imus’s victims were adults!—none of these critics condemned him. Many of them even defended him, arguing, in the ethically tone-deaf way, that lots of other comics had made tasteless jokes about Palin and her family.

What was the difference between what Imus had done and what Letterman did? Letterman claimed, plausibly, that he hadn’t meant the joke to apply to Palin’s younger daughter, but rather Bristol, her older daughter who famously was pregnant out of wedlock during the presidential campaign. (Bristol, by the way, is no older than the basketball players.) But Letterman’s joke was scripted, while Imus got in trouble extemporaneously—the defense of “I didn’t mean it the way it came out” is far more reasonable for an ad lib than for something written on a cue card. Imus apologized, but Letterman refused to apologize initially, saying, essentially, that may have been a bad joke but that Palin should shut up and live with it.

Again: What was the difference? One thing: Sarah Palin is a conservative politician who rubs liberals the wrong way, so they don’t care whether her daughter—-who is not a public figure and is not a proper target for any national commentator—is mistreated. If a joke, even one made at the expense of her minor daughter, bugs Sarah Palin, good. And if a young teen is humiliated and debased by a late night comic’s crude remarks, well, she should have chosen a more politically correct mother. That, my friends, is disgusting, hypocritical, and despicable.

No, I don’t think Letterman should have been run off the air like Don Imus, who had been living dangerously close to the line of racism for a long time and for whom this was, undeniably, the last straw. But if the critics of Imus had a milligram of fairness or integrity that wasn’t poisoned by ideological bias, they would have supported Palin, a woman and mother who was appropriately standing up for her daughter. They don’t, and they didn’t. Back to Dave…]

Letterman brushed off Palin’s foul call, saying the joke wasn’t about her daughter…later, he claimed that he didn’t even know that any of Palin’s daughters were with her at the game. But when a comedian makes a joke about a public figure going to a baseball game with her daughter and the daughter being sexually assaulted there, and it turns out that the figure’s daughter really was at the game, then the comic cannot logically or reasonable still claim that the joke wasn’t about the daughter who really attended the game. His intent doesn’t matter, at that point. A week later, when Letterman finally did apologize on the air, this concept is what he claims he suddenly understood.

Nonsense. Letterman’s pants, about which he frequently jokes, were on fire. He’s a smart man, and he had to know his initial joke had missed its mark and hit an innocent bystander…and Letterman didn’t care. Like the media critics and women’s advocacy groups who don’t think that a 14-year-old girl whose virtue was impugned by a TV star was worthy of as much support as 19 and 20-year old college athletes whose character was insulted on a morning radio show, Letterman doesn’t think the people he disagrees with politically—or their teenage daughters!—deserve fair, civilized or respectful treatment. To make this crystal clear, he followed up his botched A-Rod joke a few nights later with a joke about “Gov. Palin’s slutty flight attendant look.”

Then, to Dave’s dismay, the criticism of Letterman began to grow and take hold. Conservative talk-show hosts and blogs were like a dog with a bone, and the more the story was circulated, the more fair-minded Americans of all political persuasions became annoyed with Dave’s callousness. With a new rival, Conan O’Brien, in the Tonight Show chair, Letterman’s CBS bosses undoubtedly told him it was time to wave a white flag and pretend to be decent, and he did. His apology was rambling, uncomfortable, and, to my ear, palpably insincere, but it was an apology. Palin accepted it.

But we learned something about David Letterman, if we hadn’t come to this conclusion already. He’s not a nice guy, he’s not a fair man, and he’s a bully.

And I’m not laughing at him any more.