Matt Damon and John Krasinski ran into a big problem while making their film “Promised Land”; how they solved it tells us a lot about Hollywood.

Some time ago, the two actors decided to make a movie about fracking — a method of getting once-inaccessible oil and gas out of the ground that has become the bête noire of many environmentalists.

The two wrote a screenplay they said was about “American identity . . . and what defines us as a country.”

It was the usual Hollywood script. We all know the . . . drill: Damon’s character works for an “evil” oil company. He comes to small-town America and sells locals a dangerous bill of goods.

Then he encounters two problems — his corporate heart is melted by an attractive local woman and Krasinki’s character, an environmentalist, reveals the oil company plan to exploit, pollute and leave.

Shocked townspeople feel betrayed. Damon is conflicted — will he go with the company and his career, or with his heart and ride back into town in his white SUV, denounce the oil company and save the day?

The filmmakers were so pleased with the script that they announced it would be promoted as a potential Oscar winner.

But then came trouble.

I broke the news that “Promised Land” was about fracking and now I can reveal that the script’s seen some very hasty rewriting because of real-world evidence that anti-fracking activists may be the true villains.

In courtroom after courtroom, it has been proved that anti-fracking activists have been guilty of fraud or misrepresentation.

There was Dimock, Pa. — the likely inspiration for “Promised Land,” which is also set in Pennsylvania. Dimock featured in countless news reports, with Hollywood celebrities even bringing water to 11 families who claimed fracking had destroyed their water and their lives.

But while “Promised Land” was in production, the story of Dimock collapsed. The state investigated and its scientists found nothing wrong. So the 11 families insisted EPA scientists investigate. They did — and much to the dismay of the environmental movement found the water was not contaminated.

There was Wolf Eagle Environmental Engineers in Texas, a group that produced a frightening video of a flaming house water pipe and claimed a gas company had polluted the water. But a judge just found that the tape was an outright fraud — Wolf Eagle connected the house gas pipe to a hose and lit the water.

Other “pollution” cases collapsed in Wyoming and Colorado. Even Josh Fox, who with his Oscar-nominated documentary “Gasland” first raised concerns about flammable water, has had to admit he withheld evidence that fracking was not responsible.

These frauds and misrepresentations created huge problems for the Damon/Krasinski script about “what defines us as a country.”

So, according to sources close to the movie, they’ve come up with a solution — suggest that anti-fracking fraudsters are really secret agents employed by the fossil-fuel industry to discredit the environmental movement.

In the revised script, Damon exposes Krasinski as a fraud — only to realize that Krasinski’s character is working deep undercover for the oil industry to smear fracking opponents.

Hollywood is worried about declining theater audiences; it’s blaming the Internet and the recession. But the real problem might be closer to home.

Damon and Krasinski said they were making a movie that “defines us as a country” but then shoehorned ideology into a script — and when real-world events became a problem, they shoehorned in more ideology.

The simple truth about fracking is that much of the opposition is being driven by proven liars, charlatans and fraudsters — some driven by zealotry, others by hunger to win a big lawsuit.

There is a war going on in parts of America between impoverished locals and urban elites. These elites are using fraud, exaggeration and celebrity star power to stop rural communities from prospering through gas drilling.

Sounds like a great setting for a movie. Unfortunately for America, it’s not one Hollywood is going to make anytime soon.

Phelim McAleer is a journalist and the director of “FrackNation,” a documentary about fracking.