“All Governments Lie: Truth, Deception, and the Spirit of I.F. Stone” is an urgent and fascinating documentary. Even if you belong to the choir it’s preaching to, it has the rare distinction of being a movie you can agree and argue with at the same time. The title makes it sound like a portrait of I.F. Stone, the trend-setting investigative journalist (he died in 1989) who in his highly influential self-published newsletter, I.F. Stone’s Weekly, tweaked and railed against the sins of the U.S. government — and the mainstream media, though back then it was known simply as, you know, journalism — from the early ’50s through the early ’70s. Stone, you could argue, was the missing link between Thomas Paine and the Internet. “All Governments Lie” treats him as the original political blogger, though it doesn’t offer much more than a thumbnail sketch of Stone. His gadfly spirit hovers over the movie, but his life and work occupy maybe 10 minutes of it.

We see Stone in clips, where he looks like a jovial owl in Coke-bottle glasses, wearing the outfits of a portly professor, and he explains his reporting methods, which were so unsexy at the time that they now seem completely exotic. He didn’t call government officials, and he wasn’t even accredited to attend a White House press conference. Instead, he went into back rooms and pored through documents and transcripts to learn what was really going on.

The result? In 1964, when President Lyndon Johnson and his Secretary of Defense, Robert McNamara, engineered the Gulf of Tonkin incident, the two contrived acts of North Vietnamese “aggression” that were used as a trigger to launch the war in Vietnam, the mainstream media didn’t discover or acknowledge the truth — that the U.S. had misrepresented the incident — for years. But I.F. Stone got to that truth the week after it happened, one of countless scoops he nailed while under the mainstream radar. In the movie, Michael Moore compares Stone to Toto in “The Wizard of Oz,” tugging back the curtain to reveal the power elite hiding behind their image of authority. It’s a comparison that Moore takes comfort in, because it means that we don’t have to be so frightened of what’s behind the curtain.

I.F. Stone, known as “Izzy” (the perfect rock-star-of-dweeb-investigators nickname), was one of the great journalists of the 20th century, and he deserves a movie of his own. But “All Governments Lie” is mostly devoted to the pluck and courage of his present-day inheritors. It’s a portrait of roughly half a dozen independent reporters, a few of whom have achieved notoriety, who are carrying on the tradition of renegade muckraking that Stone almost singlehandedly put on the map in the postwar era. The Intercept, an on-line investigative site, was launched in 2014 by Glenn Greenwald and Laura Poitras (from “Citizenfour”) along with Jeremy Scahill, with financial backing from the eBay founder Pierre Omidyar. Greenwald calls it “The spirit of I.F. Stone, but funded with $250 million,” and the site has done a great deal to unearth the new surveillance security state, including a story we see about the use of German satellite towers to coordinate assassinations by U.S. drones.

The movie tips its hat to people like Amy Goodman, whose global news program “Democracy Now!” straddles radio, TV, and the Web, and John Carlos Frey, who we see reporting a cataclysmic story about 200 Mexican immigrants whose bodies were discovered in mass graves in Brooks County, Texas, 70 miles from the border. Mostly, though, “All Governments Lie” focuses on big game like the rah-rah run-up to the Iraq War, which it uses to illustrate the thesis that the mainstream media — all of it — has become a bought-and-paid-for tool of government and corporate power.

On dark days, there’s a good case to be made for that. The propaganda that paved the road to the war in Iraq (the acceptance of WMDs, the Colin Powell testimony, even the preposterously alleged Saddam/Al-Qaeda “connection”) went, for the most part, egregiously unquestioned by the mainstream media, notably The New York Times. That has now made the Iraq War drumbeat a kind of Rosetta Stone for independent journalism. Yet as you watch “All Governments Lie,” the anti-mainstream-media arguments are repeated so often, and so broadly, that they become a kind of catechism: All media is controlled by advertisers. Reporters aren’t allowed to question The System. Greed, corruption, and government-sanctioned criminality are shrouded in narcotizing fake news. There’s truth to all of this — especially if you tend to get your news from network TV. But if you’d just arrived from Mars and watched “All Governments Lie,” you’d come away thinking that independent journalism in America was the only kind of journalism you could trust. And that, to put it mildly, is an overstatement.

One of the reporters featured in the movie is Matt Taibbi of Rolling Stone (which, the last time I checked, was part of the mainstream media). Taibbi is indeed a great reporter, and the film salutes him for taking on the titans of the financial industry with a certain bombs-away ‘tude. (It’s a tone that echoes Stone’s sarcastic wit.) Yet the news that he’s uncovered doesn’t necessarily speak truth to power any more than the reporting you regularly see in, say, The New Yorker. (He just brands himself as an upstart more than Jane Mayer does.) In the movie, Michael Moore tells a story about how he went to visit I.F. Stone in the mid-’80s, and Stone told him that when you’re reading the newspaper, you should skip the front page and go right to page 17, where the real action is. But another way to put that is that if it’s on page 17, at least it’s in there. The question is: Wherever it’s placed, will you get people to read it? If the Donald Trump era has taught us anything, it’s that the mainstream media can be woefully irresponsible (e.g., exploiting Trump’s every utterance for ratings), but it can also be incisive and exploratory in ways that don’t always make a difference.

Directed by Fred Peabody in a mode of lively documentary prose, with Oliver Stone as one of its executive producers, “All Governments Lie” suggests that the kind of fearless independent reporting practiced by I.F. Stone is alive and well — and that if anything, it’s gaining traction. The film’s arguments about the blizzard of fake news (the Kardashians, etc.) that swirls around us are undeniable. At the same time, the fragmentation of our attention spans — and the general dislocation from reality — that has led to a society engulfed by conspiracy theory, not to mention an “outsider” presidential candidate who lies more often than the government does, can’t be blamed on mainstream media. The problem is more profound than that. In the movie, Glenn Greenwald, the investigative heir of I.F. Stone who has arguably fallen closest to the tree, is correct when he says, with trademark eloquence, “The entire system breeds a certain orthodoxy, it breeds a certain kind of range of pieties. And if you deviate too far from them, it will reject you.” What he’s saying is probably true of the media in virtually any society: It will never undermine the system that’s the basis of its reality. The question is whether that’s corrupt, or whether it’s just life.