Moviegoers who see the documentary “Merchants of Doubt” couldn’t be blamed for leaving the theater in a cynical mood.

Directed by Robert Kenner (the Oscar-nominated “Food, Inc.”), “Merchants of Doubt” pulls the curtain back from spin doctors who present themselves as experts in the topic of the day, and even as scientists knowledgeable in specific fields.

But these experts may be hired guns for industries seeking to shape public opinion. Millions and billions of dollars may be at stake.

There’s much information in “Merchants of Doubt’s” 93 minutes, too much and to the point of redundancy. Streamlining would have delivered the filmmakers’ message more effectively.

Kenner based “Merchants of Doubt” on Naomi Oreskes and Erik Conway 2011 book, “Merchants of Doubt: How a Handful of Scientists Obscured the Truth on Issues from Tobacco Smoke to Global Warming.”

Oreskes and other spin doctor-disputers appear on camera. So do spin doctors who regularly bring their misdirection to CNN, Fox News, other news outlets and even courtrooms.

Kenner frames the spinners and counter-spinners with a real-life magician, Jamy Ian Swiss. Sleight-of-hand card tricks are his specialty.

“It offends me when someone takes the skills of my honest living,” the magician says, “and uses them to twist and distort and manipulate people and their sense of reality and how the world works.”

The film covers years of denial by the tobacco industry and other industries. Some especially strong scenes feature Chicago Tribune reporters Patricia Callahan and Sam Roe. Their investigative work resulted in an award-winning series about toxic-flame retardant chemicals. Unfortunately, such deep, time-consuming reporting happens less and less in today’s budget-constricted news culture.

On the other side, the film’s alleged ministers of misinformation include Marc Morano. He’s executive director of ClimateDepot.com, a leading site for climate change skeptics.

On camera, the delighted Morano describes the work he’s done to discredit scientists as “a lot of fun. We mocked and ridiculed. … I’m not a scientist, although I do play one on TV occasionally. OK, more than occasionally.”

The industry-backed groups in the film that send Morano and his peers to spread their messages include the Center for Consumer Freedom (financed by fast food companies); Citizens for Fire Safety (founded and financed by flame retardant chemical manufactures); and the Non-Smoker Protection Committee (funded by RJ Reynolds Tobacco).

“Merchants of Doubt” devotes much of its 96 minutes to climate control. Climate-change doubters aren’t likely to see “Merchants of Doubt” and, if they did, they’re unlikely to change their minds. The film finds a wealth of worthy interviewees but it probably will preach to the choir on the one hand and be ignored by the other.