Documentarian Robert Greenwald's flashy films have been described as "liberal pieces of agit-prop," but in his latest film "War on Whistleblowers: Free Press and the National Security State," both the Obama and George W. Bush administrations are in his crosshairs for their lack of transparency and their willingness to make examples out of whistleblowers in a post 9/11 world. And there's a big pond to fish from: nearly a million people have top-secret clearance, according to the film.

Greenwald has previously made documentaries about Fox News, Wal-Mart and the Koch Brothers under his advocacy organization Brave New Foundation, but he insists everybody and everything is fair game, so long, he says, as he's exposing weaknesses in the system. I spoke with him earlier this week about the "War on Whistleblowers."

EXCERPTS:

CNN: What was the catalyst for this project?

Greenwald: We became aware of the crackdown on whistleblowers. It was troubling but it didn’t seem at first blush like there was enough for a film. Then through research and reading, we began to realize that the crackdown on the national security whistleblowers was directly related to the power, influence and expansion of the national security state. One of most important elements was every single whistleblower that we interviewed told a version of the same story, which is they’d seen something, they’d heard something, they realized they could not in good conscience remain silent, they tried to reach out, they tried to report, going through channels where they worked and they came up against a stone wall. And what each one of them did was they turned to the press. FULL POST