This is really not that hard to believe. I don't know why people are calling it a hoax. If you read the FBI pamphlet that has been circulating for years asking that any "defenders" of the Constitution, super "patriots", etc be reported to the FBI as right wing extremists (they also include a list of left wing extremists groups) it has a lot of similarities to this document.
Even if this document turns out to be fake, which I think is highly doubtful, if you don't believe that similar documents exist, you're asleep. <IMO>