Imagine, for a second, that you don’t exist. Not in any meaningful sense of the term, anyway. You have consciousness, you have awareness, but no body, no sensation, no emotion. Like that scene in The Matrix where Neo wakes up in that vat of slime and realises he’s basically one fancy battery among millions.

One day, you’re offered the chance of a vessel to experience the world as we know it, with all its beauty and colour. You will be able  to feel, touch, smell, eat, have sex, run, walk, feel the rain on your face and the warmth of the sun as the clouds pass above you. The catch? Your body is vulnerable and as capable of feeling pain as it is pleasure. Your life may last eighty years, it may last six minutes. You may suffer and die horrifically. You may be tortured, raped, starved, sick, disabled, poor. You may be born  into wealth and security and do nothing but sate your own appetites.

Would you take the chance?

It’s a bit heavy for a Thursday afternoon, but it turns out that an existential crisis is the best possible side effect to watching Joshua Oppenheimer’s ‘The Act of Killing.’ Less welcome side effects? Thoughts of violent revenge, helplessness, a realisation that humanity is basically loathsome and you’re a terrible, terrible person for living a relatively comfortable life and not doing me to help those in need. I’ll stick to the warm, familiar sensation of existential crisis, if it’s all the same to you.

Released in 2012, The Act of Killing is a documentary exploring the Indonesian killings of 1964-65. As Oppenheimer explains at the start, after the failed coup attempt by the 30th September Movement, people who didn’t subscribe to doctrine were dismissed as communists and it’s believed the purge that followed resulted in the deaths of approximately half a million Chinese people, left wingers and intellectuals.

Oppenheimer initially sought to tell the story via the testimony of the victims of violence and their relatives but after a few weeks of filming the army intervened and wouldn’t let them participate. The survivors suggested Oppenheimer approach the perpetrators – many of whom still live in proximity to the villages they ravaged – as they would be able to tell the story too.

The result is an almost hallucinatory mix of vivid colour, emboldened masculinity and unspoken sadness that articulates the banality of evil more effectively than anything I’ve ever seen.

At face value, these men look like the idiots you see swaying down your local High St of a beautiful summer evening. Swollen with hubris, they strut through the documentary describing the methods they used to kill and maim, round up and rape, invade and burn, with a thousand yard stare of relish and tip of the tongue resting unconsciously on their lips as they recall anodyne details no one would make up, because what would be the point? In the movies, no one worries about the fact that gallons of blood shed on a concrete floor and left to bake in the heat very quickly starts to smell. So Anwar Congo, movie ticket scalper turned death squad leader, demonstrates how to kill efficiently and with a minimum of bloodshed for the camera.

Later, when watching the footage back, he shows regret. “I would never have worn white pants [to kill],” he sighs.

The difference between these guys and your average street hoodlum obsessed with gangster movies is timing. Anwar and his jovial sidekick Herman Koto were selling tickets to movies when the government needed street muscle. What, in most lives, would be dismissed as weakness seeking the trappings of power, was harnessed, indulged and encouraged. These men, and the many that join them in the re-enactments used to tell the stories, aren’t smart or suave, Machiavellian or sartorially elegant. They’re stupid, self-obsessed and utterly deluded.

Nothing like the form we’ve been led to believe evil takes.

Nominated for the Best Documentary Award at the Oscars and critically acclaimed, The Act of Killing wasn’t universally applauded. Nick Fraser, editor of the superb BBC Storyville documentary strand, felt it tasteless to have murder deconstructed by gleeful, apparently unashamed perpetrators and resisted pressure to show it.

“I find the scenes where the killers are encouraged to retell their exploits, often with lip-smacking expressions of satisfaction, upsetting not because they reveal so much, as many allege, but because they tell us so little of importance.

Wouldn’t it be better if we were told something about the individuals whose lives they took?”

Nick Fraser is clearly a better judge of documentaries than I am. But I disagree with this assertion, made in a Guardian interview in February 2014. I think these scenes tell us a great deal about humanity; far more than popular culture, which renders the victim of violence disposable while simultaneously inflating the glamour of killing. Horror and suffering have become an abstract, and the more that happens, the easier it is to disassociate ourselves from it and push it to the back of our minds.

The Act of Killing left me feeling bereft for a while. I’m an atheist, so the comfort blanket of an afterlife to redress the unfairness of life is not mine to embrace. The uncomfortable truth that these men have tortured, raped and massacred thousands, and yet remain free to ponce around playing dress up and leering at women shipped in to fulfill their sordid whims while families can only watch, the space from which their loved ones were torn from them gaping between them unacknowledged.

Almost two hours into the documentary, a re-enactment of a village being burned to the ground is shown. Deputy leader of the structure of the ministry of youth and sports Sakhyan Asmara turns up and issues a rallying cry to the participants, telling them to ‘improvise‘ during their mock pillage and ‘express themselves‘. Afterwards, perhaps realising that an incumbent politician appearing in a film encouraging such activities might not scan well internationally, he tells the crew and crowd that what they’ve just done is not ‘characteristic of their organisation‘ and ‘looking like they want to drink blood‘ is ‘bad for their image‘.

No kidding.

I’m not a masochist. I don’t enjoy feeling awful. But how am I different from Asmara if I shield myself from the reality, comforting myself with the conceit that because I’m safe, everyone else is?

We should question ourselves sometimes. It’s our obligation to those who’ve suffered to remember how fortunate we are.