This question came to mind when listening to CBC Radio One's The Current this morning. This morning they were reading letters in response to a segment last week on conspiracy theories. Today's segment included a brief talk with Barry Zwicker, a Canadian freelance journalist who has been promoting the theory that 9/11 was a US government plot. He claimed that the idea Osama bin Laden could have pulled off the September 11th attacks from a cave someplace with a laptop is the least credible theory. Others have made that statement as well. But why? Does it have anything to do with the fact that bin Laden is an Arab? I can't help but think of various theories that ancient peoples didn't build the great works such as the pyramids and so on, that instead it was mysterious "others" who did. I often get the impression that those theories are sometimes driven, even if only subconciously, by racist ideas since those ancient wonders were built by "brown" peoples. I've never heard of anyone trying to claim ancient Greek and Roman wonders were built by aliens or the inhabitants of Atlantis, and I would guess in many cases this is because they're seen as "our" anscestors, are perceived as being "white."
Would we be hearing as many "they couldn't possibly have done it" claims if 9/11 had been pulled off by Japanese cultists, say Aum Shinrikyo? After all the Japanese have a society and economy seen as directly equivalent to Western industrial ones. I haven't seen conspiracy theories about Aum's attack on the Tokyo subway, claiming say that someone gave them the nerve gas they used, and this is probably for the obvious reason that people expect there would be some kooks in a highly industrial and technological country like Japan with the education and skills to cook up nerve gas in their kitchen. Compare this with Saudi Arabia and other Arab countries, which are perceived as primitive and ignorant backwaters. This of course ignores the fact that bin Laden was of the monied class in Saudi Arabia, the kind of folks who get access to Western technology and education. Bin Laden himself has degrees in civil engineering and economics/public administration. In other words this is not some hick who doesn't have a clue about anything other than being violent, and we know the kind of damage even those kind of people can cause. His educational background sounds exactly like the kind of thing that would make coming up with a plan like the "offical" version of 9/11, and making it happen, completely plausible. It certainly sounds more plausible that theories that for example would require sneaking tonnes of explosives into the structure of the World Trade Center without anyone noticing something very weird was going on.
Addenda: It should also be noted that bin Laden probably wasn't hiding in a cave before the US attack on Afghanistan, given that he was there as a guest of the Taliban government.