This whole subject is extremely close to home for myself, but I'll try to be as objective as possible.
Sure there were probably plenty of things that could have been put into effect in order to prevent the 9/11 attacks, I'm not saying that they were un-preventable. BUT to say that the American government planned and executed the mass murder of thousands of its citizens is absolutely ridiculous. Why would they want to? It would have had to been panned mostly under the Clinton Administration, seeing as Bush was barely in office. Why would a president plan something so the man behind him could come forth as the "oh fearless leader" that Bush did? Of course homeland security could gave been stepped up earlier, and the FAA could have been more strict on policies earlier, but I think any thought that the US government was part of it, is ridiculous.
Also, if you ask me, all of those who stand at Ground Zero and chant how it was an "inside job", and how "the US had it coming" should all be lined up and shot. I don't care what your stance is on the events, but to stand where thousands DIED and yell that they had it coming, and trying to undo any comfort that had been brought to the families and relatives mourning makes you a douchebag who should burn in perdition.