http://en.wikipedia.org/wiki/Paul_Craig_Roberts#September_11.2C_2001_attacks
For instance:
Roberts comments on the "scientific impossibility" of the official explanation for the events on 9/11 and says those engineers and physicists who accept this theory are wrong. On August 18, 2006, he wrote:I will begin by stating what we know to be a solid incontrovertible scientific fact. We know that it is strictly impossible for any building, much less steel columned buildings, to “pancake” at free fall speed. Therefore, it is a non-controversial fact that the official explanation of the collapse of the WTC buildings is false
In addition:
Roberts is seriously dismayed by what he considers the Republican Party's disregard for the US constitution. He has even voiced his regret that he ever worked for it, avowing that, had he known what it would become, he would never have contributed to the Reagan Revolution.
Yet he gives no specifics nor proof. We know? What do we know? How do we know? Definitely disinformation.