There are gradations of guilt and complicity. There is no evidence the Saudi state is complicit in 9/11, nor that it is sheltering OBL or the important al-qaida people. There is no lack of evidence that individual Saudi's are part of the OBL/al qaida network, and we could reasonably guess that the Saudi state is not turning its own country upside-down in a hunt for OBL cronies. That is quite different from the role of the Taliban in re: OBL and al qaida. The logic of linking support for some bombing in Afgh to bombing S.A. unfolds absurd conclusions from a fallacious analogy. I think this is an easy argument.
I am more bothered by Chomsky's argument that the U.S. should be bombed for what the Clinton Admin did to the Sudan or Iraq. My best answer is that there is no agency capable of using force against the U.S. on behalf of good that is inclined to do so. As I said once before, if there was some giant Sweden intent on curbing U.S. excess, my national loyalties, such as they are, would be under some stress. But that's a purely academic question.
The U.S. is the one and only superpower. The use of force against it in a military sense by anyone or anything is out of the question. Any such force can only exert pressure by being exerted on innocent Americans, which makes it unacceptable. It isn't fair, but that's the way it is.
mbs