Mark Kleiman seems to me to have the goods on this one:
If you had any doubt that the fuss about Libby's sentence is largely a matter of Washington insiders, political and journalistic, rallying to the defense of one of their own, consider the contrasting silence about the Siegelman case. A highly popular Democratic Governor of Alabama was indicted by a highly political U.S. Attorney's office, which is now seeking a thirty-year sentence. He was convicted of appointing someone to a state board that the same man had been appointed to by three previous governors, in return for a contribution in support of a referendum campaign.
As Mark notes, rewarding campaign contributors with ambassadorships -- to say nothing of policy concessions -- is common. And the case seems at least a little fishy ("the fact that Siegelman was convicted of corruption in the course of fighting against Jack Abramoff, Abramoff's his Indian-gaming clients, and Abramoff's buddy, now the Governor of Alabama, may be merely ironic") on a few grounds. But even if there's nothing fishy about it, 30 years is a sentence for a vicious murderer, "And not a peep of protest from the Washington Post, which instead is running a non-stop campaign of whining about Scooter Libby's thirty months."
As a sidebar, it's not even clear to me how Libby came to be a member of The Establishment in such good standing. I have it on good authority that he was in arrears on his dues to Temple Rodef Shalom before any of his legal troubles even started going down.