One of the reasons why conspiracy theories about the U.S. government have to be taken seriously, at least some of the time, is that much of what the government does and knows is kept secret from ordinary citizens.
There's a movement that's been launched to declassify 28 pages from a Congressional report on the 9/11 attack.
President George W. Bush censored 28 pages of this report—an entire section said to describe the involvement of specific foreign governments in the attacks. After reading it, Congressman Thomas Massie described the experience as “disturbing” and said, “I had to stop every two or three pages and rearrange my perception of history…it’s that fundamental.”
Much more here.
Hat tip: Justin Raimondo, who wrote an opinion piece about the matter. It is somewhat speculative, but one easy way to prove him wrong would be to release the secret information.