The statements of Osama and many of the juristic Saudi Arabian and Afghani islamic scholars regarding the validity and support of the attacks were enough for me.
Anyone who wants to claim that the support for 9/11 given by radical Arab community as well as many of the more reactionary scholars, as well as the community of jihad that sprang up online in the face of Al-Qaeda organization and the popularized movement, must make the argument that not only does the US control or is allied with the despised Saudias, Egyptians, and Yemeni governments, but also the militant right wing in the same vein.
If the US was under direct control of both sides of the Arab political spectrum, forcing them to alternately publish their writings and views supporting 9/11 in Arab-only milieus while simultaneously pressuring the apostate Saudi and Egyptian governments to give out their (very common among US-Friendly Middle Eastern Govts.) "Osama kinda sucks Lite" version of condemnation, fuck, why even try?
The Arab reaction to 9/11 has been very....for lack of a better word, "Arab", in terms of what could be expected in light of the politics and sociology of the region. The hyperbolic, somewhat inane statements about Osama bin Laden as a "simple man" and "one who asked others to lead prayers" and the sort of "friendly, stupid" guy theory put out by the Saudi Royals and supported by Mubarak, the identification with the radical jihad, and the alternate love/hate for Osama in Arab regions is not something which could have been cooked up. No US-Europe conspiracy theory conglomerate could have fabricated what was a very Arab reaction to a "very Arab" phenomenon.
Whether or not Osama and Al-Qaeda caused 9/11 (Which I very strongly believe they did), the polarizing effect and the "movement", so to speak, have progressed just as if they would have had Al-Qaeda succeeded in some other form of Anti-US attack. The stated goals of Al-Qaeda and the other (tending to be very minimal) anti-US Arab groups have followed a very predictable, very linear pattern which has drawn from the same ideological base and profited from the same inertia which now propels Arab support, either directly through recruitment, or through funding, of anti-US "terrorist" conglomerates such as Al-Qaeda and other pan-Arabist or pan-Islam movements which tend to be centralized around the Palestine movement.
In other words, even if 9/11 was a complete hoax perpetrated by the US, it had the same effect and the same stated goal as did every other associated terrorist initiative.