Anti-Public Intellectuals, or Public Anti-Intellectuals?

Over at The Atlantic, Richard Posner writes:

I am concerned with the fact that academic economists, when they become either public officials or public intellectuals (like Krugman), leave behind their academic scruples.

In a later paragraph, he expands on his theme:

This raises the question of the ethical responsibility of academic economists, such as [CEA Chair Christina] Romer (and Krugman, and Lawrence Summers, and many others), who write for the media or join the government, either to adhere to academic standards in their nonacademic work or to make clear to the public that they are on holiday from those standards and that what they say in their public-intellectual or governmental careers should not be thought identical to their academic views.

And then, with an astonishing lack of awareness of the irony involved, Judge Posner — who is also a highly-regarded scholar at Chicago Law School — spends the rest of his article opining on the economic effects of the stimulus.
Yes, this is the same Judge Posner who has never, as far as I can tell, received any training in macroeconomics. Having recently re-read much of the modern literature on fiscal policy, I found myself underlining several of his claims that either reflect an incomplete understanding of the issue or are simply at odds with the current views of mainstream macro. Yet they are stated as simple truths, with no hint of qualification. And he cites not a single number nor builds a serious theoretical argument in support of any of his conclusions.
In fact, it’s a fun game to read his whole piece (available here) and assess just how far Posner falls short. Post your favorites to the comments.
Update: At Economist’s View, Mark Thoma begins by listing the obvious shortcomings; Brad DeLong finds at least seven major problems; and over at EconBrowswer, Menzie Chinn piles on, finding six-and-a-half major shortcomings. And for eagle-eyed readers, there are still more problems waiting to be highlighted; let’s call it an intellectual “Where’s Waldo?”
Finally, an aside: This isn’t about which side of the debate Posner is on; on the substantive issue of whether fiscal stimulus is worthwhile, I actually agree with Posner. No, it’s about the very issue Posner raises: how to engage in serious economic debate.