I know the episode your talking about and remember the message. It's probably no coincidence that Nixon split his guts to David Frost in 1977. The FBI under J.E. Hoover had been spying on US citizens for decades, they routinely infiltrated and sabotaged non violent groups such as anti-war protesters, as an example of how absurd it became they had a huge dossier on John Lennon. I'm not an American but I was 17 at the time and watergate was a huge affair, it was clear that the kind of thing that happened at the Watergate hotel was routine, the scandal was followed by some significant legislation on what data government could collect, and under what circumstances domestic groups could be infiltrated.
It doesn't seem to have worked, I would not be at all surprised if someone found a similar dossier on the "Dixie Chicks" buried somewhere in Homeland security's basement.
As an Aussie I would like to give Letterman a pat on the back for what he's been doing with his "stooge of the day" segment, regardless of your views on gun control, the point he keeps hammering home is that all the stooges voted in direct opposition to the expressed wishes of an overwhelming majority of their constituents. Every single stooge on Letterman's show is a specific example of an individual politician doing their bit to "steal your liberty". Sure politicians should lead rather than follow the opinion polls, but when they are so out of kilter with them (in some cases taking a position opposed by over 90% of voters), they have some 'splaining to do.