On last night’s The Late Show with David Letterman, the “chicken-hearted and gutless” (though he won’t speak for Conan O’Brien) host ripped on NBC executive Dick Ebersol, suggesting he focus on picking out sweaters for Olympics anchor Bob Costas instead of miring himself in NBC’s late-night disaster. Letterman’s not going to stop mocking Leno, either. “I’m telling jokes and making fun of Jay Leno relentlessly, mercilessly, simply for one reason: I’m really enjoying it.” [CROWD APPLAUDS WILDLY.] “It’s just fun!”