"To me, the idea that news has to have novelty has lost its lustre," he told me this week from his New York office. "If a story is resonant enough to dig into, it means that it has some lasting value. If you look at the Wikileaks film four years from now, there will still be a lot that will be valuable."
It is hardly surprising that Gibney would find Wikileaks attractive material: he typically zeroes in on subjects - the collapse of Enron; the torture and murder by US soldiers of an innocent taxi driver in Afghanistan; clerical sex abuse - in which secrecy is common currency. But he says his films are about secrets "hiding in plain sight. I look at subjects that have been very publicly covered and find that things are not always as they seem.
"It's the occupational hazard of journalism. When a scandal hits big, there is a rush to get material on the air or in print. Everybody's trying to be current. As a result, mistakes get made, things get missed, and later on you can see things you might not have seen in the hustle and bustle."
The first three words of the film's title are provocative - they certainly provoked Wikileaks founder Julian Assange, who tweeted that they were "unethical and biased" - given that they do not represent Wikileaks' mission statement. They are, in fact, uttered by former NSA and CIA director Michael Hayden, when he's explaining what US intelligence agencies do.
Gibney admits he was being provocative, but also trying "to set Wikileaks inside a broader context".
"The rich irony of that title is even more present now that Snowden has told us how many secrets the US Government is stealing, not only from foreign countries, but from its own citizens. But that's what journalists do all the time: they go out and they try to get public officials to give them secrets. Assange took [the phrase] in a narrow legalistic way; he may not have as much of a sense of humour as I gave him credit for."
Wikileaks has posted online an annotated text of the film, rebutting its claims at almost every turn. Gibney is unfazed.
"Nothing in that document makes me feel that we didn't get something right. What does concern me is that a lot of people will read the document instead of watching the movie. Furthermore, it isn't the film. Somebody made an audio tape recording of a screening, but, as you know, all of Manning's words [which consist of reproductions of encrypted online chat; we never hear his voice] are left out. A quarter of the film, the heart of the film, is missing.
"It was a ham-fisted attempt at damage control, which came off as a disinformation campaign, designed not to stimulate debate but to shut debate off and discourage people from seeing the film. It is not exactly consistent with their idea of transparency."
Gibney did not secure an interview with Assange - the extensive footage is all second-hand - but says he "never stopped trying". At the end of filming, he says, the pair had a six-hour meeting, in which Assange said "the market rate" was $1 million.
"He wanted some kind of transaction that proved that he was in control, that he had the power. I was okay with that - I said no because I don't pay for interviews - but what I found more reprehensible was that he asked me to spy on the other interview subjects [many of whom are detractors], and report back to him and then maybe we could talk about an interview."
Early in the film, Assange flashes a smile and says, "I enjoy crushing bastards." But even if you share his view of who the bastards are, his "damn the torpedoes" approach comes across as chilling: at one point, he says he would happily publish a recipe for anthrax; at another, he explains his failure to redact from the Afghan War Logs the names of innocent civilians with the throwaway line "if an Afghan civilian helps coalition forces, he deserves to die".
"He had no harm-minimisation process at all," says Guardian journalist Nick Davies, who worked with Assange on the worldwide release. Gibney agrees.
"He's much more doctrinaire about this issue than I am comfortable being. You have to make judgments about whether the revelation of secrets will cause personal damage that is out of proportion to the public value of publishing the secret.
"It throws into question the whole moral calculus of leaking. It's very easy for governments to say, 'We're for democracy; we're for truth and we have to do some pretty nasty things to protect that, including stealing people's secrets.' The problem is that, once you start to go down that road, you start to feel like you have an inviolable right to do whatever you want because you're on the side of righteousness and goodness."
He is mindful that Assange has long championed the idea of the "noble lie" - his early hacker alias, Mendax, alludes to the "splendide mendax" [noble untruth] of Latin poet Horace.
"That's where Assange started to go wrong. He isn't launching wars, but he is a powerful figure. He has a big bully pulpit, and for him to then assume that because he's on the side of good, it's okay for him to lie and do unethical things, that doesn't fly.
"I don't think," says Gibney, "that it's to anyone's benefit for him to speak lies to power instead of truth to power."
Defrocking the Vatican's cover-up of abuse
Alex GibneyAlex Gibney's other film in the festival line-up is a meticulously composed and damning story of a protest against and a cover-up of sexual abuse by a priest in Milwaukee in the 1960s. Its title, Mea Maxima Culpa: Silence in the House of God, is particularly resonant because the boys concerned were all deaf: in their long pursuit of justice, they have made a lot of noise, and the church's response has been deafeningly silent.
As with the Wikileaks film, Gibney knew he was treading territory that many might think well-trodden; but he says the men's lawsuits had uncovered documents "that enabled you to trace a specific crime in a specific place all the way to the top and show that it was a systemic problem."
The church would always say it was an American problem or an isolated problem or a few bad apples. This film gives the lie to that excuse: this was systematic and the cover-up was handled in the Vatican.
The film is lent currency by the February resignation of Pope Benedict XVI. As Cardinal Joseph Ratzinger, he was the man on whose Vatican desk all the sex abuse cases worldwide ended up - and stayed. And it plainly invites the conclusion that it was more than frailty that caused the Pontiff to renounce the office.
"Let me be charitable and say I hope his conscience was troubled by the scandal," says Gibney, who was raised in the Catholic faith. "Perhaps he felt that the one positive contribution he could make after failing the church so badly for so long was to resign, which is something no Pope had done in 600 years."
He holds out no hope than Pope Francis will do any better.
"I don't see him doing what is needed, which would be to disgorge all the documents, to say this was not only a sin, it was a crime and we are going to take responsibility for that sin and that crime.
"I think the Catholic Church is going to have to start from the bottom up. People are going to have to make their own Catholic Church and stop giving money to the Vatican, because that's where the problem is. They are not willing to reckon with the abuses of their own power."
• The New Zealand International Film Festival runs from July 18 to August 4 in Auckland, and later in other centres.
