On "The Late Show" this week, David Letterman debuted a rather unfunny segment about "TV disclaimers," or the warnings you see before shows begin. Most commonly, viewers will see "Parental discretion advised" with a TV-14 or TV-MA tag applied in bold print across the screen. Dave, though, with all his hip and wily ways, added what he considered more pertinent information for fans of the most boring CBS shows on air.