Appearing on CNN Sunday, documentary filmmaker Robert Greenwald said that his latest film will highlight the Obama administration's ongoing "war" against people who reveal the government's embarrassing and sometimes shocking secrets.

"War on Whistleblowers: Free Press and the National Security State" documents the Obama administration's efforts to silence and retaliate against whistleblowers, and the effect that overreaching government secrecy has on journalism.

A trailer for the film features journalists from The New York Times and The New Yorker explaining that there's a shortage of investigative news because so many whistleblowers are worried that they could face prosecution for dishing the dirt on the ill-dealings of power.

"We hope, by having these incredible journalists speak out, we call attention to the fact that literally the Espionage Act is being used against whistleblowers," Greenwald said Sunday. "Calling whistleblowers spies is really, in many ways, beyond the pale of anything we've seen from any other administration."

Host Howard Kurtz countered by asking why Greenwald, a liberal, was so adamant about criticizing the Obama administration on this issue.

"President Obama is doing a terrible disservice to democracy, to free speech and to the power and importance of both whistleblowers and journalists," Greenwald said, adding he agrees with the assessment that Obama is likely "too close to the CIA."

"As [New York Times reporter James] Risen says, we can't have a democracy without a strong free press," he said. "In the national security arena, these people are really heroic. They're speaking up, they have nothing to gain, and they're protecting us against fraud and abuse."

This video is from CNN, aired Sunday, April 14, 2013.