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.
To accept the official announcements of the story of 9-11 is instantly satisfying in several ways. Commercial airliners, hijacked by suicide terrorists, flew into buildings at the behest of a really smart master-terrorist named Osama Bin Laden. This is an immediately credible scenario""many of us had heard the name Bin Laden, and "knew" he was a terrorist who lived on the other side of the world. Indeed, the WTC had been attacked once before. And terrorism itself certainly exists--both sides of the 9-11 controversy can agree on that. So, to accept the official announcements that followed the attacks enabled you quickly to locate all the blame for the attacks in a tiny evil army of foreigners, all out of immediate reach, but accessible to the U.S. Army, you bet. The hijackers themselves were all dead, and their leader was extremely hard to find, but American forces could find and punish them. No need, really, to conduct any investigations or solve any mysteries--an evil super-hero with a small army of mentally enslaved unfortunates was able to penetrate the defenses of the finest air force in the world to murder 3000 Americans. A fluke, but in life and in sports, stuff like that happens.
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.
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.
It's entirely understandable that any American should believe the official 9-11 story. And, of course, to consider seriously for an instant that there could be something seriously wrong with that story, to imagine that as possible, really does change everything, just like 9-11 itself. If there's a chance that Americans colluded in those horrors, then the entire mental structure of our sanity, which we've lived in all our lives, has a serious crack, a San Andreas Fault, right down the middle. If we think it possible that "We have met the enemy, and he is us," then everything previously unthinkable is thinkable.