Conspiracy theories don't require "belief." People, groups, organizations and governments conspire all the time. It's their natural state. Which is why criminal law throughout the world recognizes the crime of conspiracy.
Just read one link, read about Operation Northwoods. And once you read that the Joint Chiefs of Staff proposed false flag terrorist attacks on American targets to provoke & justify conflict with Cuba, then you realize the government is capable of anything. Then consider it was proposed in 1962 and wasn't made public until 1997. Thirty five years. Then extrapolate all the things going on now that you won't find out for years, if ever.
via Reddit: (nsarchive.wordpress.com)