There can be no debate with Holocaust deniers. That is a core principle of moderating the AskHistorians subreddit, one of the largest history forums on the internet—and a crucial lesson Mark Zuckerberg seemingly does not understand. Zuckerberg got into hot water on Wednesday when he stated that Facebook wouldn’t necessarily remove Holocaust deniers from its platform because people “get things wrong” and because it’s not always possible to understand the deniers’ intent.

This position fundamentally fails to grasp how Holocaust deniers spread anti-Semitic propaganda, underscoring a flaw in how the purportedly neutral platform thinks it ought to handle particularly odious ideas. Conversation is impossible if one side refuses to acknowledge the basic premise that facts are facts. This is why engaging deniers in such an effort means having already lost. And it is why AskHistorians, where I am one of the volunteer moderators, takes a strict stance on Holocaust denial: We ban it immediately. Deniers need a public forum to spread their lies and to sow doubt among readers not well-informed about history. By convincing people that they might have a point or two, they open the door for further radicalization in pursuit of their ultimate goal: to rehabilitate Nazism as an ideology in public discourse by distancing it from the key elements that make it so rightfully reviled—the genocide against Jews, Roma, Sinti, and others.

Taken together or separately, these beliefs serve one goal: to make the ideas of the Nazis socially acceptable.

Clarifying, as Zuckerberg later did, that Facebook would remove posts for “advocating violence” will never be effective for a simple reason. Any attempt to make Nazism palatable again is a call for violence. More than 11 million victims prove that. Because Holocaust deniers want and need a platform to reach this goal, it is imperative to deny it to them, as an institution, a newspaper, or a social media forum.

AskHistorians is unique among public-history outreach projects. Readers ask questions about historical subjects ranging from ancient history to the modern day, and people with proven expertise in that particular subject—working historians—answer them with in-depth and comprehensive answers supported by scholarly sources.

AskHistorians is unique in another way. It shares a social media host, Reddit, with a number of communities that have become notorious for their toxicity, such as the Pizzagate conspiracy theorists, the misogynists of the Red Pill, and the pro-Trump trolls of The_Donald. The subdivided but shared platform exposes our group of moderators to a daily barrage of sexism, racism, white supremacy, and Holocaust denial. Due to these circumstances, the AskHistorians team decided very early in the now-seven-year history of the forum to implement rules addressing this problem. While the early rules had included the provision to “be polite,” a sudden influx of users from the then-active Stormfront subreddit—a community for neo-Nazis—led one moderator to impose strict rules against content that is sexist, racist, or anti-Semitic in nature. This was greeted with unanimous consensus by the team of moderators that continues through today.

We remove content that is racist, sexist, or anti-Semitic in nature and ban the offending users from commenting in our forum on a daily basis. While our rules are also designed to combat content like the denial of the genocides against American Indians, Armenians, and others, as well as talking points such as slavery revisionism, Nazi Germany and the Holocaust are two of the most popular subjects on our forum. Questions in these fields often attract scores of Holocaust deniers. This frequent interaction has again and again proven to us that Holocaust denial is a form of political agitation in the service of bigotry, racism, and anti-Semitism. It has also taught us a lot about the strategy of Holocaust deniers online and that the only effective way to stop them from spreading hate and lies is to refuse to give them a platform.

The content we encounter most often corresponds almost directly with the most commonly held beliefs and positions of deniers, as summed up by historian Richard Evans:

• The number of Jews killed by the Nazis was far lower than 6 million.

• Gas chambers could not have been used to kill large numbers of Jews.

• Hitler and the Nazi leadership did not pursue a program to mass-murder Jews or were unaware of its existence.

• The Holocaust is a myth invented by a Jewish conspiracy.

Taken together or separately, these beliefs serve one goal: to make the ideas of the Nazis socially acceptable. The Holocaust is the obvious proof that the ideology of National Socialism is, at its core, racist, anti-Semitic, and genocidal. Holocaust denial erases this massive crime to blunt the horror of Nazi ideas as a whole.

The methods we have seen Holocaust deniers use in order to distort, minimize, or outright deny historical facts all demonstrate that they don’t merely “get things wrong.” Denialists in our subreddit will often point to self-proclaimed revisionist historians as their sources. Even the medievalists and classicists among us have by now become familiar with the arguments of David Irving and Fred Leuchter. These alleged historians feign sound historical practices by citing sources, only to leave out key passages, obfuscate facts, and ignore proper historical context. To make their positions less odious at first glance and to fake legitimacy, these deniers claim the attractive title revisionist.

It is, of course, a rhetorical smoke grenade.

Actual historians engage in interpretation of historical events and phenomena based on the facts found in sources. When new information, or a new interpretation, emerges and is considered in light of existing knowledge, that is revising earlier thought. “Revisionist” Holocaust deniers do not revise; they twist the truth and peddle lies to advance their political agenda.

But more insidious, more frequent on both our forum and the internet at large, is the technique known as “just asking questions”—in internet parlance, “JAQing off.” Designed to further Holocaust deniers’ aim of spreading their talking points, this involves (a) framing a denialist talking point in the form of a good-faith question and (b) calling for “open debate.” This lends itself well to the question format of our subreddit. Inquiries about what materials were used for gas-chamber doors, why early editions of Elie Wiesel’s Night don’t mention gas chambers, why the death toll of Auschwitz allegedly changed over time, or simply what proof there is for the Holocaust (discounting all testimony and postwar material) might seem innocent at first glance. They are not. They are designed to call often minor details into question and to create doubt among readers less familiar with the history of the Holocaust. Deniers want to provoke an audience into making the mental leap of “If this detail is suspicious, what else might be wrong?” This is a Trojan horse for a slide from denial into hatred. When we remove such contributions, what deniers will inevitably do is to call for “open debate” and sling accusations of censorship and violations of free speech.

In this endeavor, deniers focus on many minor and obscure details and leave out crucial context. It takes them little effort to formulate a wrong assertion, but it takes historians a long time and a lot of words to refute one. Our early attempts to engage on these points have shown that length and nuance do not play well on the internet and do not interest the deniers. The point of JAQing off is not to debate facts. It’s to have an audience hear denialist lies in the first place. Allowing their talking points to stand in public helps sow the seeds of doubt, even if only to one person in 10,000.

This particular tactic of disguising denialist positions as innocent questions and bolstering their dissemination with calls for open debate has become dramatically more prevalent since the advent of the internet, but it isn’t particularly new. In the early 1990s, Holocaust deniers affiliated with the so-called Committee for Open Debate on the Holocaust, or CODOH, placed a large number of full-page ads in college newspapers across the United States titled “The Holocaust Story: How Much of It Is False? The Case for Open Debate.” CODOH already wielded the ever-popular rhetorical strategy of attacking “political correctness” in universities and claimed that it suppressed their viewpoints. The ads succeeded. They sparked an intense debate about free speech and the alleged necessity to provide all views (their views) a platform. The Holocaust deniers of CODOH portrayed themselves as victims of alleged censorship and, at the same time, spread their message through seemingly innocent questions and demands for debate.

Discussing the ad campaign in her essential book Denying the Holocaust, Deborah Lipstadt highlighted the naïveté of those who believed that the “light of day” would dispel the lies of the deniers. “Light,” she wrote, “is barely an antidote when people are unable … to differentiate between arguments and blatant falsehoods.” Lipstadt ended by darkly observing that “correctly cast and properly camouflaged, Holocaust denial has a good chance of finding a foothold among coming generations.”

That prediction comes closer to reality with every post using denialist rhetoric on Twitter, Facebook, and Reddit. The intentions behind those posts don’t matter. To gauge whether a person is malicious or merely “ironic” is a futile exercise, for to give Holocaust deniers’ positions a platform is to disseminate their propaganda. To draw the line at overt calls for violence is equally insufficient. Holocaust denial serves Nazism, and Nazism is an ideology that at its very core advocates for violence. The only way to fight this morally and factually wrong viewpoint is to deny these positions a platform. This is the crucial lesson we have learned in running the AskHistorians forum. It is the lesson other platforms must emulate if they are sincere in fighting racism, anti-Semitism, and Nazism.