Letterman to O'Reilly: 'I'm Not Smart Enough' to Debate War --It didn't take long for fireworks to erupt last night when Fox News Channel's Bill O'Reilly guested on David Letterman's "CBS Late Show," with the late night host finally admitting he wasn't "smart enough" to engage in a debate over the Iraq war. The verbal fisticuffs began when Letterman asked if O'Reilly had a good holiday. O'Reilly responded: "I had a nice Winter Solstice," prompting a contentious exchange over whether Christmas traditions were indeed under attack. But the confrontation really heated up when Letterman suggested, "Let's talk about your friends...