It is not just about Sarah Palin. Think of Palin as the canary on the coal mine. This battle is part of the war between the Jacksonian strain of American politics and the "mediated democracy" that has evolved over the last couple of decades.
It is that Jacksonian strain that sets America apart. It has given us some of our greatest presidents-- Jackson himself, Lincoln, TR, Truman, and Reagan. It fuels our military strength. It is a vital component to our political economy.
Without it we might look a lot like Europe: sclerotic, corrupt, and military impotent.
With a mediated democracy, those with the right resume and right friends are never called to account for their mistakes and corruption. Jamie Gorelick, Barney Frank, Larry Summers, and Chris Dodd can create mess after mess and yet,, they remain members of the club.
Contrast the unrelenting stream of abuse hurled at Sarah Palin with the silence that surrounds the gaffes of crazy Joe Biden.
Palin was a dangerous outsider; Biden is a member of the club's DC branch. Plus Biden was selected by The One.
The Letterman attacks were just the latest demonstration that the club will sink to any level to repel outsiders. All that concern for civility? That only applies to those inside the charmed circle.
So the issue is not Sarah Palin. Any effective outsider will get the same treatment. (E.g. the Tea Parties, Joe the Plumber, Carrie Prejean).
There is a political calculus at work as well. America remains a nation where neither Left nor Right commands a majority. Surprisingly, the Right is still larger than the Left.
The natural equilibrium, therefore, is Center-Right.
The Left has only one effective tactic. They must demonize and marginalize the RIght. They must make the Right an anathema to moderates so that those in the center support the Left.
That's why resercons are so valuable to the members of the club. and liberals in general.
For resercons in waiting, bashing conservative outsiders is a sure way to get the attention of the membership committee of the Guild of People Who Really Matter. R. S. MacCain has discussed this repeatedly-- most recently here.