Professor Bainbridge has a point, in a narrow sense. Groupthink by itself did not cause any of the problems, no matter what the Senate Report says. As should surprise nobody, I don't believe that any single factor or issue "caused" the intelligence failures. One can as easily blame poor education funding, which leads to poor and even absent exposure to foreign languages and culture, which in turn leads to inability to create and process human intelligence and intercepted communications. (My own bias here is probably pretty apparent…) One can as easily blame simple careerism—the recognition that promotion opportunities, and often even continued employment, depend upon satisfying one's boss, and that one's boss is all too often a political appointee (or protegé of a political appointee) whose agenda may not always mesh with uncomfortable truths. One can easily blame the doublethink of defining "allies" based upon the immediate economic self-interest of a small portion of the electorate; and, to be perfectly clear, this is more than just "environment good—oil companies bad," as the oil companies probably aren't even the most egregious motivators.
No, the intelligence failures both before and after 11 September 2001 are too complex for any 500-page exegesis. And reducing such a document to a soundbite or twenty is, as the Perfesser implies, just going to end up as support for somebody's faddish management-theory approach. I remember "TAC Brown" paint all too well. One doesn't change underlying cultural biases (both in the broad sense and in a particular organization) by embracing new fads; or at least one doesn't do so without alienating everyone who doesn't buy that particular fad.