This is a documentary about Christianity in America through the lens of one man. But with a twist: the filmmakers are perplexed that people of faith actually wholeheartedly believe in God and and work to uphold Biblical values in politics.
From what I can tell, the folks at AP/Frontline think that Christians should go to church on Sunday, but then behave secularly in their careers and in politics, because their faith is supposed to be padlocked inside a church building.
But this type of thinking only makes sense to atheists, and I'm not convinced that they are truly this naive. I see this as propaganda, because there's no good-faith attempt to see that Christians understandably want a voice in government, just like everyone else.