last heir to the old tradition of "tonight show" and somebody who is not only comfortable interviewing heavyweight figures but in recent years has been delivering himself of various opinions. him and rachel maddow the other night talking about same-sex marriage. >> i'm just sick and tired and it has come close across the line of nonsense. this ongoing, politically nuanced, religious discussion of gay marriage, gay rights. it is absolute stupidity. >> so, is letterman the last quote serious late night comic? >> i think so. there is a core of seriousness that makes him surge above his competitors at moments of great national import. after 9/11, he was the guy everybody turned to. the first guy everybody wanted to hear how he would frame it because we were told irony was dead. we were told humor would never be the same. letterman carries the whole tradition in his head.