A video clip featuring William Friedkin recently experienced a small level of virality among online film circles, in which the film-maker dresses down Nicolas Winding Refn after the younger director declares his own film Only God Forgives to be a masterpiece. Friedkin repeatedly calls for a medic, compares Refn’s film unfavorably to Citizen Kane, and most memorably, uses a vivid metaphor that puts the “anal” in “analogy”.

Friedkin, speaking on a drizzly afternoon in his suite at New York’s Carlyle Hotel, wants to make it clear that he bears no ill will to Refn. “I like him! He’s a nice guy. I like him very much.” But the larger truth underlying their charged exchange persists: William Friedkin simply does not give a damn.

He’s aged 82 now, and seven years out from the release of his last film. (That was 2011’s chicken-fried neo-noir Killer Joe, a classically Friedkinian work in its marriage of extreme, lurid material with tightly controlled aesthetic rigor.) He’s on the press circuit once again because he’s finally got a new film to promote, an entirely self-funded documentary titled The Devil and Father Amorth. The project dips back into Friedkin’s past as the man behind The Exorcist, chronicling the real-life purging of a demon by a Vatican higher-up. Skeptics will be tempted to place the words “real-life” in scare quotes, and the film doesn’t mount a particularly convincing case as to why they shouldn’t have that caveat. It’s here that Friedkin’s blithe disregard for what the general public thinks emerges as the source of all his power; believe him or don’t believe him, it’s all the same as far as he’s concerned.

In the spring of 2016, while in the town of Luca to receive a prize for his achievements in the world of opera, Friedkin wrote on a lark to a theologian friend in Rome requesting an audience with the pope or, failing that, the official papal exorcist. Much to his surprise, the reply came in the affirmative, and he had an audience with Father Gabriele Amorth one week later. Friedkin had spent 45e years throwing scripts about demonic possession in the garbage, but the prospect of capturing the genuine article proved too tempting. He used this meeting to lodge a humble request: if it wouldn’t be too much trouble, could he record an exorcism?

Father Amorth allowed Friedkin and a small, unobtrusive handheld videocamera in the room while he attempted to free an area woman named Cristina from the clutches of an unnatural force, their ninth such session. Friedkin related the extraordinary events of that day in a feature for Vanity Fair, but the footage sat unused. “For a long time, I had no idea what I was going to do with this film,” Friedkin says. “I had it, but it was like a home movie. So I decided to bring it to medical and psychological professionals to see if they could debunk it, or explain it using terms from their fields.”

Friedkin expanded the footage to feature length by supplementing with interviews from experts, some less credulous than others, and one follow-up that sees him returning to Italy for a check-in with Cristina. While they were visiting a cathedral, she descended into an intense fit of madness complete with bodily contortions and speaking in tongues – except that Friedkin didn’t bring his camera into the building to catch it, so he can only describe the experience in voice-over paired with shaky B-roll of the empty church. He alleges to have stared the devil in the face, but the audience will just have to take his word for it.

“You’re not suggesting that I made this up, are you?” Friedkin goes right for the jugular when he smells the faintest whiff of doubt. “I understand that there’s room for skepticism. I’m not a skeptic. I don’t make films or move through my life as a skeptic. I’m not interested in skepticism, that’s something you’re either born with or acquire as you live … You don’t know a damn thing, and neither do I. Nobody knows if there is an afterlife, a heaven or hell. What is our purpose here? Nobody knows that! We have no idea!”

For anyone else, selling an exposé as questionably founded as this would be an exercise in circumlocution, obfuscation and half-truths. For Friedkin, however, the best defense is a good offense. His sincere and total lack of concern for winning anybody over enables him to talk through the issues instead of around them.

“I’m not interested in convincing you, or anyone else,” Friedkin explains. “This is what I saw, and the only way to deal with that conclusion was in this way, getting closure through this film. You’ll have to work that out for yourself.”

It should come as no great shock that Friedkin doesn’t read his reviews. He’s opposed to the very concept of formal criticism – he used to read James Agee, but considers Pauline Kael an “overeducated fool” – positing that the only people truly qualified to assess the quality of a film are those who have made one themselves. “Any schmuck with an iPhone is a film critic today. What qualifies someone to be a film critic? Why should I believe one person’s review over another’s? What would prompt me to accept criticism?”

He extends this doctrine of thick skin from his work to himself. At a time when the tide appears to be turning against directors prone to extreme, unorthodox methods – Quentin Tarantino, Lars Von Trier – the notoriously intense Friedkin has drawn some heat for past behaviors, and he’s not having it. He was known to fire blanks from a prop gun to get a realistically shocked reaction from some actors, and slapped another in the face before one take on The Exorcist. Ellen Burstyn sustained an injury to her tailbone during production, and has described Friedkin as a demanding collaborator in recent interviews looking back on the film. He tells it like this:

“[Ellen Burstyn] never lost a day’s work, let’s put it that way. There was no insurance claim, and she’s worked steadily ever since. I’m sure she was hurt by the fall – you fall on your backside, it’s gonna hurt – but she wasn’t injured. And for that I say, thank God.”

Friedkin comes from an older school of directing, where getting the shot sometimes took priority over all else. Cantankerous and proud, he’s never been one to sugarcoat his words, and he has no intention of refashioning himself as a pillar of sensitivity for a sensitive age. Even after expressing distaste for Harvey Weinstein, he refuses to play the role of moral arbiter.

“I don’t want to discuss that. That’s not what this is about. Are you asking me if I’m refreshed to hear about Harvey Weinstein or any of these people? That’s not the point of this interview at all. He’s had his criticism, and continues to have it. That’s not why I agreed to do this interview, and I hope that if you use this quote, it reflects that. I’m not here to talk about the Me Too movement, as much as I’m sure you’d like me to.”

For Friedkin, this hardline insistence on setting his own rulebook has fueled a career spanning five decades and ensured that his films remain fiercely original even as his résumé continues to grow. He divulges that he’s currently writing a new script, though he can’t provide any details at this early juncture. When it comes, audiences can be sure it’ll be another unmistakable product of William Friedkin’s feverish, uncompromised imagination. But of course, whether you think so could not be of less consequence to him.

“If you’re going to make a film or an album of music or a painting, you cannot afford to stop and think what other people will think of it. You’ve got to take into consideration what your editor thinks, if, say, you’re a writer. But I don’t have anyone to answer to. I make a film because I want to. Sometimes they’re successful, sometimes they’re not, but the way I think about my films is always very personal … I’m very happy to be alive. Life is a great gift that I don’t take for granted.”

• The Devil and Father Amorth is out in the US now and in the UK later this year