Will all the folks who believe the U.S. government played an active role in 9/11 please read this Popular Mechanics article? Please? There are actual real-world problems worth protesting in Union Square. (Yeah, I know that folks who believe conspiracy theories have a pathological drive to avoid evidence which counters what they believe and to seek only that "evidence," which reinforces what they already believe*, but ... a man can hope, can't he?)
There's also an excellent NOVA documentary which details exactly how the WTC towers fell - without being demolished. And please let's dispense with the "no building in the history of architecture had ever collapsed this way" argument, shall we? No building had ever had a jetliner full of jet fuel crash into one of its upper stories, creating the pancaking effect, which NOVA's documentary describes in explicit detail. It doesn't take a degree in physics to understand what happened.
*I feel like there's a whole doctoral thesis waiting to be written on this subject, only someone's probably already done it. The principle applies in general to human beliefs, I think, not just conspiracy theories.