Is Libertarianism Discredited?

So sayeth Jacob Weisberg: Sure, he allows, there were lots of contributing causes to the current meltdown, but "market fundamentalism" deserves the lion's share of the blame, and having brought the world to the brink of a Great Depression, libertarians should have the decency to just shut up from here on out.

Now, I have my disagreements with libertarians now and then, but this strikes me as an uncommonly silly idea. (Almost as silly, one might venture, as the idea that Bristol Palin's pregnancy discredits social conservatism.) I'd direct you to Brink Lindsey, Tyler Cowen, John Schwenkler and of course Will Wilkinson for more on the broader issues, but I want to focus in on this one paragraph from Weisberg's piece:

The argument as a whole is reminiscent of wearying dorm-room debates that took place circa 1989 about whether the fall of the Soviet bloc demonstrated the failure of communism. Academic Marxists were never going to be convinced that anything that happened in the real world could invalidate their belief system. Utopians of the right, libertarians are just as convinced that their ideas have yet to be tried, and that they would work beautifully if we could only just have a do-over of human history. Like all true ideologues, they find a way to interpret mounting evidence of error as proof that they were right all along.

To which the rest of us can only respond, Haven't you people done enough harm already?

But see, the thing with Marxism was that every single time someone actually tried to implement its tenets, the result was mass murder and large-scale impoverishment: There weren't any examples, save in fantasyland, of a Marxist regime that wasn't an economically-incompetent tyranny. So for Weisberg's analogy to work, libertarian principles would need to have produced misery more or less steadily, across multiple regimes and cultures. But all he's got is one crash, which has followed on the heels of decades of impressive economic growth (with very little mass murder, I might add), which almost certainly won't come close to wiping out the gains of the last thirty years, and which has a sufficiently tangled etiology to make any monocausal explanation deeply, deeply suspect.

Now obviously the crash isn't good news for defenders of deregulated markets. But we're a long way from Pol Pot territory here, I think. And arguing that a single bad economic contraction following a long period of growth permanently discredits an ideology that can be implicated in both the growth and the contraction is like arguing that, say, Weimar Germany permanently discredits partisans of democracy. (Good God, it led to Hitler! Haven't you people done enough harm already?)