Late Thursday night, after hours of vacillating, the media finally agreed on how to handle the video shot by the chief suspect in the New Zealand mosque shootings. The consensus was more or less organic: It would be reckless to show it.

As of Friday, the massacre is considered the deadliest attack aimed at Muslims in the West in modern times, with 49 dead and 20 seriously injured.

Soon after the gunman’s footage was live-streamed on Facebook on Thursday evening, clips tore through the internet, as YouTube, Twitter and Facebook all tried in vain to contain them — and police issued warnings against sharing the video. Images from it also showed up on traditional media outlets, before they thought better of it.

But should we really be “protected” from footage that documents white supremacist terrorism as vividly as anything can?

At other times in history, such documentation — whether by a professional or bystander — has been considered necessary and urgent, and to look at it without flinching has been thought a duty of citizenship.

Consider the newsreels of concentration camps at the end of World War II, which left no doubt that the Nazi project had been genocide.

Later, Nick Ut’s widely disseminated 1972 war photos of 9-year-old Kim Phuc (“Napalm Girl”) running from her destroyed village in Vietnam — naked, burned, desperate — displeased President Nixon, who tried to claim they were “fixed.” They weren’t, and the photos helped pierce public denial and build opposition to the Vietnam War.

Over the last few years, with extremist racism on the rise, a state of denial on the far right tends to kick in before even the bodies are buried. Already, Rush Limbaugh and his ilk are turning Nixonian, trying to twist the facts of the slaughter in New Zealand.

The far right, of course, is also scrambling to distract the public from the suspect’s sympathy for their anti-immigrant rhetoric — and his avowed admiration for President Trump.

“There’s an ongoing theory that the shooter himself may in fact be a leftist who writes the manifesto and then goes out and performs the deed purposely to smear his political enemies,” Limbaugh said.

There is no such theory.

Photojournalism, including film, is a key element in exposing the horror of war, violent crime, terrorism, subjugation, and even genocide.

In the New Zealand case, the perpetrator’s manifesto laid bare his extremist beliefs. But the gory video is what demonstrates the consequences of that ideology.

When white supremacy is thought to live only in words, it becomes abstract, mutable, even deniable. The very real extensions of that ideology are easy to ignore.

It’s in this context that the importance of excruciating documentary films like Alain Resnais’ 1956 “Night and Fog,” a 32-minute film about the mass murder of Jews during the Holocaust, becomes apparent. The French government periodically re-airs “Night and Fog” as a public service: to remind people of the horrors of war. Even some American high schools in the ’80s used to show it to make the devastation wrought by racists with weapons indelible in the hippocampus.

The videographer of the 2019 massacre in New Zealand was hardly Alain Resnais, of course. It was the gunman himself. Driven by the bigoted madness he expressed in his manifesto, he did not bring a historian’s eye to his film; he brought a murderous subjectivity.

The gunman’s 17-minute video was styled as a violent first-person-shooter rampage on the model of Doom. According to the writer Maria Konnikova, Doom, the monstrously popular video game that set the standard for such games, supplies “a virtual environment” that lets players feel “absolute presence and happiness” as they mow other figures down with their virtual semiautomatics.

Those aiming to suppress the gunman’s video of the mosque shootings worry that, in watching it, viewers might inadvertently taste the rapture of a Doom-like environment. Further, they might crave for themselves an actual first-person, real-life experience of mass murder.

The New Zealand shooter may have hoped for that too.

Perhaps that is why he broadcast shatter-shot bullets and digital video at once, choreographing the deaths of dozens for the camera as he beamed them to the world on Facebook.

He confided in one of his simpatico cells online that he was done with merely posting bile; he wanted to slaughter people. And while he killed, he was still on the internet, offering spoken marginalia as he carried out his carnage, like a gamer on Twitch.

A few outlier news organizations are still broadcasting some massacre footage, though it has now been edited, reframed and narrated to drain it of propaganda effects.

In one Turkish version, an unseen narrator asks: “Who among us keeps watch from this strange watchtower to warn of the arrival of our new executioners?”

The same might be asked, around the world, as security in mosques is tightened and mourners congregate in New York and London and Bangladesh, though no one seems to hold out much hope that a next execution can be prevented.

Virginia Heffernan writes for the Los Angeles Times.