David Letterman has a long running late night program that is part of CBS' entertainment division. Katie Couric is the anchor of the CBS Evening News, a program produced in the news division.
Despite his decades in broadcasting, Letterman seems unaware there is an important difference between the two divisions. John McCain cancelled an appearance on Letterman's show scheduled for Wednesday night, likely thinking it was a bad night to make small talk and joke around with the talk show host.
But McCain did appear at CBS Wednesday afternoon to be interviewed by Couric. Letterman seemed insulted by this. After all, when you earn over $40 million a year for delivering mediocre comedy to ever-smaller audiences, politicians are supposed to come on your show to pay homage. So Letterman went off on a petulant rant about McCain, even stooping to a Metamucil joke.
These kind of old people jokes have been Letterman's staple throughout the campaign, so this is no great surprise. Originality and creativity disappeared from this show long ago. Letterman is now 62 years old, so how many more years he is going to be able to make jokes about the infirmities of age without wincing?