It occurred to me that I haven't seen anyone examine the mental comforts of conspiracy denial, using the handy tools of amateur psychology. It's my guess that there's considerable comfort to be had, especially for men, from an acceptance of the official explanation for 9-11. This is not to say that many women aren't happy with the Arab hijacker theory, but for men, the provision of a clear enemy to fight is always especially gratifying.
The fact that this reads like a comic book plot doesn't seem to be a source of embarrassment for the anti-truther movement. In fact, an evil mastermind who, through mindless suicidal drones, wreaks havoc on good and decent people is the major plot driver of The Lord of the Rings, and many other fantasy and science fiction epics. Mythically speaking, it's golden.
And under the broad strokes of the main story, there's also a layer of historically accurate information that supports the main plot line. Joe and Jane Six-Pack would accept the unadorned story eagerly, but there's something to satisfy the more thoughtful as well. The back story is that American foreign policy for the last 30 years could easily result in some very unhappy Arabs. CIA meddling in the politics of Iran and Iraq, and above all, our support for Israel, have been highly unpopular on the Arab street. Well-read people could find the anti-American sentiments of the terrorists quite credible, if regrettable.
So the psychological comforts of the official story are several and real: you get a clearly defined enemy, a simple solution to a complex foreign policy problem, you get to feel morally superior to your enemy because you're more civilized and don't kill civilians, and finally, if you know something of the history of American policy in the Near East, you get to feel superior to those who don't.
In fairness to their enemies among the truthers, the conspiracy deniers should admit that there is much psychological comfort in their own position, and that conspiracy theorists do not have a monopoly on convenient but deluded assumptions. 9-11 is, after all, a heap of facts, and it is open to human inquiry. Whether the heap was created by our enemies' hatred or something worse has yet to be decided.