There’s a smoking gun in “Risk,” Laura Poitras’ scrappy, tossed-together documentary about hanging out with Julian Assange, although it has nothing to do with leaked documents or scurrilous government behavior. It has to do with the revelation of Assange’s psyche. The movie, which finally opened this weekend, was shot starting back in 2010, shortly after Assange came to prominence as the founder of the renegade website WikiLeaks. It’s clear that Poitras thought she’d signed on to catch the inside story of a freedom fighter whose cause aligned with her own. Before long, though, a monkey wrench gets tossed into the vérité manifesto when Assange is accused of sexual assault by two women in Sweden. Those accusations, now seven years old, worm their way into the center of the movie.

A murky cloud of confusion still hangs over the acusations. Assange, who has never been formally charged, has always maintained his innocence (he claims the accusations were made after incidents of consensual sex), and there has long been an implication of conspiracy from the left about it: Was it a massive frame-up devised by one or more of the institutions that Assange attacks? That said, there’s a telling scene in “Risk” in which Assange talks to his lawyer about what strategy to take during a court appearance, and during the conversation he suggests that his accusers are part of a radical-feminist conspiracy. If he’s innocent of the accusations, he certainly has the right to be angry, but he still paints with an awfully broad brush. His tone is hostile and high-handed, one might even say piggish.

The most revealing moment, though, comes later on. Sitting around and talking, this time more casually, Assange asserts that the sex case marked the first time he became truly internationally famous. His notoriety from WikiLeaks, he says, turned him into a celebrated — and persecuted — figure among the media and power elite. But it was only after the scandal that the larger world caught up to who he was. Then he grins slyly and makes a joke that’s somewhat shocking: He says that it might be good if he was hit with another sex scandal every six months or so.

Cinema vérité really does have its value — it doesn’t always probe, but it reveals — and what it captures here is how Julian Assange says this with a smirk of pleasure that indicates how addicted he is to his own fame. At that moment, he comes off as the flip side of Donald Trump: a pure creation of media who pretends to care about this or that, when it’s really all about him. For most of “Risk,” Assange presents himself with a guarded and ruthless cyber-warrior pragmatism, like that of a revolutionary who’s gone past caring if he lives or dies. His persona is that of a man subsumed by his cause. Yet “Risk” captures how that cause, over time, became fused with Assange himself. The more you watch him in this movie, the more you see that he’s a kind of lizard: a frosty and calculating ego junkie, with one eye on history and the other eye on the mirror.

Assange’s ego might strike you as a minor issue if you’ve bought into his nihilist dogma, which says that WikiLeaks is a force for good in a world of superpowers launching conspiracies of such indecency that they need to be stopped by whatever means necessary. For a lot of us, it’s a tempting point of view to endorse, since it’s based on a paradigm that’s been around (and growing) for 50 years. If you consider yourself a liberal, the idea that there needs to be a basic check-and-balance on what the U.S. government does — even behind closed doors — is a core principle. Assange won credibility with his early scoops, as when he posted 39 minutes of classified footage of the July 12, 2007, Baghdad airstrikes in which two Reuters journalists were killed by US AH-64 Apache helicopters. (Assange titled the video “Collateral Murder.”)

Yet the bloom is now off the WikiLeaks rose. If the site had been called DocumentDump, that might have been a more accurate summation of the indiscriminate nature of the Assange version of journalism. And one of the oddities of “Risk” is that unlike “Citizenfour” (2014), Poitras’ dramatic and highly responsible whistleblower documentary, which caught the drama of Edward Snowden’s ethical odyssey, this new one finds itself way behind the curve of its subject’s rise and descent.

If you want to see a definitive chronicle of the Julian Assange saga, check out Alex Gibney’s superb and head-spinning “We Steal Secrets: The Story of WikiLeaks” (2013). “Risk” is the catch-as-catch-can, sketchbook version, yet it has a value, and that’s that we get to study the lizard up close. Poitras spends enough time with Assange to touch the scariest thing about him (though he would say it’s the most valiant): his cold-blooded absolutism. With his white hair, soft voice, and slightly creepy sherry-club manner, he’s sort of like Sting if he’d become an annoying Marxist philosophy professor. The key to the annoyance is that Assange voices everything with such passive-aggressive neutrality that what he’s telling us is: The WikiLeaks mission is literally beyond debate. It’s simply a fact that more transparency is good, and less transparency is evil.

Yet is that always the case? The conventional — and easy — argument to make against the excesses of WikiLeaks is that the exposure of un-redacted documents can wind up hurting innocent people, an issue that Assange is clearly cavalier about. (To him they’re just collateral damage. Or maybe one should say collateral murder.) Yet the larger argument is one that may be trickier for a liberal to make: In the only world we live in — the real world — don’t governments, in fact, need secrets? It’s a fine line indeed, but Assange’s bring-it-all-down anarchist vision, in which institutions are always the enemy, carries its own dangers. Especially when you see how his narcissistic belief in the invincibility of his judgment has, in his mind, replaced the authority.

“Risk” turns into an amusingly charged competitive triangle in which the political has become not just personal but petty. Poitras, at one point, goes off to film a mysterious hacker from the N.S.A. who has been feeding her anonymous messages (she has no idea, at that point, that Edward Snowden is going to become an icon), and Assange is royally pissed at her once the Snowden files are leaked. He wanted them for WikiLeaks! But the fact that Poitras and her “Citizenfour” colleague, Glenn Greenwald, felt compelled to use the mainstream media — principally The Guardian — to put the Snowden revelations on display is a perfect sign of why the mainstream media matters. It is, by definition, the public square of a civilized society, and so it has greater meaning as a platform. You’d think that Julian Assange would cheer that, but no. He’s only happy when the system is being burned down, and he’s the one tossing the Molotov cocktail.

How come no one ever asks: Did WikiLeaks elect Donald Trump? Of all the factors that damaged Hillary Clinton in those final months of the campaign, the hacked documents that detailed her speeches to banks like Goldman Sachs were right up there, and “Risk” offers the likely scenario that those documents were handed off by the Russians to WikiLeaks. If so, Julian Assange became, in effect, a pimp of information for Vladimir Putin’s regime. Of course, there’s an argument that says: The speeches happened. The public had a right to know. Well, yes, of course we did, but in that light why weren’t the Russian hackers stealing, and leaking, Donald Trump’s tax returns? “Risk” reveals Julian Assange to be someone who acts like he’s speaking truth to power by seizing it, when actually he’s a tool — someone whose Achilles’ heel is his underlying desire for fame, which allows him to be used. And that’s the most dangerous kind of “rebel” of all.