"Merchants of Doubt," directed by Robert Kenner, focuses on corporate spin doctors such as those who deny the existence of human-made climate change. (Courtesy of Sony Pictures Classics)

In Washington, everyone’s always pushing something.

There’s Robert Kenner, sitting in the private banquet room of a Georgetown hotel, in front of a poster for his new documentary, “Merchants of Doubt,” which he has come to town, he says, to “sell.” That choice of words is fitting. Kenner’s movie — a follow-up to the filmmaker’s acclaimed, Oscar-nominated “Food, Inc.” — is all about marketing.

Unlike that 2008 film, which took on the machinery of American agribusiness and its trafficking in junk food, “Merchants of Doubt” isn’t about a product that you can buy at the store. Rather, Kenner says, it’s about something less tangible if no less bad for you, should you swallow it. It’s sold in courtrooms and the halls of Congress, he says, on television and, occasionally, in newspapers.

Call it confusion, mislabeled as clarity.

The germ of Kenner’s latest project, a simultaneously entertaining and inciting exposé of professional charlatanism — practiced, most saliently, by those hired to make the case that global warming isn’t real, or at least that there is no scientific consensus on it — sprouted in the director’s head during the making of “Food, Inc.”

"Merchants of Doubt" director Robert Kenner, center, also directed the Oscar-nominated “Food, Inc.” That 2008 documentary cut across ideological boundaries. (Courtesy of Sony Pictures Classics)

“I went to a hearing on whether we should label cloned meat,” Kenner recalls. “There was someone there who stood up and said, ‘I think it would be way too confusing, for the consumer, to give them that kind of information.’ I thought, ‘I’ve never heard something like that before.’ It was the representative of some meat company. I looked up and thought, ‘Who could this be?’ ”

Kenner can no longer remember the speaker’s name or affiliation. But since starting work on “Merchants of Doubt,” a film based on Naomi Oreskes and Erik M. Conway’s 2010 history of corporate baloney peddlers, running from Big Tobacco to climate-change denial, he has met a lot of folks just like that guy.

“It takes a lot of . . . talent to do that,” says Kenner, pausing before the word “talent” just long enough to make a reporter think he’s about to say “cojones.”

He isn’t being entirely ironic. Kenner, 65, does admire people such as Marc Morano, a professional climate-change denier and founder of the Climate Depot Web site who is, arguably, the star of Kenner’s film. After a stint in the 1990s reporting for Rush Limbaugh, Morano worked briefly as a flack for Sen. James M. Inhofe (R-Okla.), who famously called global warming a “hoax.”

These days, Morano most often pops up on TV shows arguing against the science of climate change. In front of Kenner’s camera, Morano makes for a jocular — and weirdly unapologetic — advocate for what can only be called ignorance.

“I’m not a scientist,” he jokes, flashing a huge, telegenic grin, “but I play one on TV.”

Marc Morano, who runs www.climatedepot.com, a leading site for climate-change skeptics, in a scene from “Merchants of Doubt.” (Courtesy of Sony Pictures Classics)

He also plays dirty. In “Doubt,” Morano recounts with glee how he has published the e-mail addresses of climate scientists, subjecting them to intimidation and flaming attacks from anonymous critics. (Several of the abusive e-mails are read aloud in the film by their recipients, in an evocation of Jimmy Kimmel’s “Celebrities Read Mean Tweets” segments.) It makes for a semi-serious tone that masks Kenner’s more sobering message: We’re routinely being lied to, by people who are darn good at it.

As depressing as this may sound, Kenner hopes that “Doubt” will be received by audiences as more than a muckraking investigation of snake oil salesmen. “Hopefully,” he says, “I’m selling entertainment, as well. I didn’t want to make medicine.”

What he does want to make is change.

The director’s “Food, Inc.” reputation may help. Although he doesn’t have the name recognition of, say, Michael Moore, Kenner’s earlier film cut across ideological boundaries. After all, everybody has to eat. Kenner takes pleasure in pointing out the irony of right-wing publisher Rupert Murdoch handing out 70,000 free DVD copies of “Food, Inc.” with his Sunday London Times in 2010.

At the same time, Kenner claims that he isn’t trying to convert anyone; he’s trying to reveal the hidden agendas of those who are. “People don’t like to be lied to,” he says.

There are a few recovering global-warming skeptics featured in “Doubt.” Most notable among them is the staunchly Republican former congressman Bob Inglis of South Carolina, who lost a 2010 reelection bid after acknowledging, in a radio interview, that he had come to believe in human-caused climate change. Like a prophet without honor in his own home, Inglis is shown preaching the gospel of climate change, to the derision of some of his former supporters.

Bob Inglis, a former Republican congressman from South Carolina, in a scene from “Merchants of Doubt.” Inglis lost a 2010 reelection bid after admitting he believed in human-made climate change. (Courtesy of Sony Pictures Classics)

But Kenner doesn’t care that other global-warming deniers are unlikely to buy a ticket to his film, let alone be converted by it.

He is optimistic that the last vestiges of climate resistance will one day be swept away, likening it to the sea change that has occurred over the past several years in popular attitudes about same-sex marriage and other once-contentious issues.

“Look at gay rights,” he says. “That was a set-in-stone issue, not only with right-wingers, but with liberals, too, as recently as 2008. Marijuana is another.” Tribes sometimes do get up and move, no matter how entrenched.

But he doesn’t believe that butting heads with his most stubborn opponents will make it happen.

As Kenner sees it, on any issue, there are typically three groups: true believers; nonbelievers; and the vast, confused middle. It’s not the middle’s fault it’s confused: Kenner blames the Marc Moranos of the world, who are paid to sow not just doubt but fear. (“Fear is a big part of it,” he says.) The media share much of the blame. Kenner singles out newspapers — this one in particular — for his harshest criticism of what he calls their tradition of “false balance”: the insistence on always presenting two sides of an issue, even when there aren’t two.

“I think your paper is far less inclined to show deniers on the op-ed page these days,” he says. “That’s a big change, because they were being published continually. The fact is, that confused people, and that was a big part of the problem.”

According to Kenner, change will come, but not from those shouting at the edges of the argument. Rather, it will grow out of the confused middle, where films such as “Food, Inc.” and “Merchants of Doubt” shine light on hidden, and uncomfortable, truths.

“You’re never going to convert a third of the people right away,” he says. “But as with the civil rights movement, you don’t go to Bull Connor and say, ‘Oh, you’ve got to change your mind.’ You change the people around Bull Connor, and then Bull Connor has to change. You change the culture.”

“Merchants of Doubt” is playing at AMC Loews Shirlington 7 and Landmark’s E Street Cinema.