Jonathan Chait nails it: Glenn Greenwald Is Ralph Nader.

Greenwald, like Nader, does not believe in meliorist progress. If you are not good, you are evil. Even at the heyday of his career, when he was one of the most powerful figures in America and his brand of crusading regulation reigned nearly unchallenged, Nader was constantly denouncing congressional liberal allies for failing to pass sufficiently pure iterations:

In 1970, Nader championed a report by his staff savaging Ed Muskie, the liberal senator from Maine. Muskie, who helped engineer the Air Quality Act of 1967, had a reputation as an environmental ally, but Nader’s report called the act “disastrous,” adding, “That fact alone would warrant his being stripped of his title as ‘Mr. Pollution Control.’”

That same year, the Senate overwhelmingly passed a bill to create a Consumer Protection Agency (CPA), what Nader called his highest legislative goal. But, just days after praising the bill, Nader turned against it, saying that “intolerable erosions” had rendered the bill “unacceptable.” As Martin writes, “Without Nader’s backing, the bill lost momentum” and died in committee. The pattern repeated itself, as the CPA passed either the House or the Senate five more times over the next six years, but Nader rejected every bill as too compromised.

That is the echo of Greenwald’s suspicions of the Democratic agenda. President Obama scaled back some of the Bush administration’s anti-terror policies — torture, warrantless wiretapping — but kept in place others. One could make the case that he did not change enough, but that is not a Greenwald sort of argument. He insists that Obama is worse than Bush. Obama’s health-care reform was not just a step along the way to Greenwald’s ideal, it was a monstrous sellout that probably did no good at all (“there is a reasonable debate to be had among reform advocates over whether this bill is a net benefit or a net harm.”).

This way of looking at the world naturally places one in conflict with most liberals, who are willing to distinguish between gradations of success or failure. Nader and Greenwald believe their analysis not only completely correct, but so obviously correct that the only motivation one could have to disagree is corruption. Good-faith disagreement, or even rank stupidity, is not possible around Greenwald. His liberal critics are lackeys and partisan shills. He may be willing to concede ideological disagreement with self-identified conservatives, but a liberal who disagrees can only be a kept man.

I’d add another point: the Nader purist cult was also very effective — dismayingly so — in splitting the Democratic voting base in 2000.