It was factually wrong and morally outrageous for Israeli Prime Minister Benjamin Netanyahu to say that a Palestinian mufti gave Hitler the idea for the Holocaust. Almost the entire mainstream of historians, scholars, and politicians has now said so.

The question, though, is why he did it—and the answer is that it was an unintentional, Romney-47%-moment at which a commonplace partisan lie is suddenly revealed to the world. In Romney’s case, it was the Republican talking point that half of America depends on government welfare. In Netanyahu’s, it’s that the Israel/Palestine conflict is actually a result of Arab anti-Semitism.

There is no doubt that Netanyahu was wrong as a matter of history. Even his close allies have said he’s distorted that the historical record. Jonathan Greenblatt, CEO of the Anti-Defamation League, said in a statement that “Even if unintended, the prime minister, by his words, plays into those who would trivialize or understate Adolf Hitler’s role in orchestrating the Final Solution.”

And although Bibi has made similar claims before—calling Mufti Haj Amin al-Husseini “one of the leading architects of the Final Solution” in 2012—he has already begun to backpedal, now accusing al-Husseini merely of “encouraging and urging Hitler.”

Al-Husseini did meet with Hitler and other Nazi leaders. They had common cause against the British, and against the Jews. He was, according to a spokesman for the U.S. Holocaust Museum, “an anti-Semite and willing Nazi collaborator.”

But there is no hard evidence whatsoever that al-Husseini suggested, or even supported, the idea of exterminating Europe’s Jews. It is not even known whether he even knew of the policy. The sole source for the claim is a statement by one of Adolf Eichmann’s deputies, who surely made it to deflect blame from himself and his former master. No reputable historian believes it.

(Ironically, as Netanyahu also knows, his own father’s revisionist Zionist party openly called for a “Jewish fascism” according to the German model. It’s also true that al-Husseini was only one of many Arab leaders, not all of whom shared his views.)

So what’s going on?

First, Netanyahu’s remarks were off the cuff. The transcript of his speech at the 37th Zionist Congress makes that clear. The entire speech was conversational in tone, with corrections and colloquialisms, and the particular reference to al-Husseini was an aside.

Its context was Netanyahu talking about the “big lie” that the Israeli government is seeking to destroy the Al Aqsa Mosque—which is indeed a big lie spread widely on pro-Palestine social media. In that context, he mentioned that al-Husseini had told a similar lie in the 1920s, and by the way, al-Husseini supported the Holocaust too.

It was an aside within an aside. But precisely because it was off the cuff, it offers a valuable peek behind the curtain of Israeli nationalist ideology.

Like Romney’s comment about the 47%, comments like Netanyahu’s are made all the time on the Israeli Right. They’re meant for domestic consumption, to inspire the nationalist base. The Arabs hate us, anti-Zionism is just anti-Semitism, and most importantly, the Intifada is about Jew-hatred, not resistance to the occupation.

Such claims may seem controversial to outsiders. But they are all catnip to the American and Israeli Right, and to most of Netanyahu’s audience at the World Zionist Congress. (The congress was established by the founder of modern Zionism, Theodor Herzl, in 1897. Nowadays it is mostly ceremonial, but millions of philanthropic dollars are at stake.)

These claims are central to the ultra-nationalist narrative. Palestinian violence isn’t resistance—it’s bigotry. Thus, peace is not the answer, because it won’t eradicate the Jew-hatred. Only Jewish strength is the answer. (Of course, blaming Palestinian violence on anti-Semitism also stokes deep Jewish fears, and collective trauma about the Holocaust.)

This was the ideology of Ze’ev Jabotinsky, the founder of revisionist Zionism (and the fan of Jewish fascism) as well as Netanyahu’s own father. Force is all the Arabs understand, because they hate Jews and will keep hating Jews no matter what.

As Netanyahu said in the same speech, “The real reason we have this terrorism is not because the terrorists are frustrated in the peace process. They’re frustrated because there’s a State of Israel and that frustration will continue.”

And further, “The core of the conflict was the desire to destroy the Jews anywhere: without a state, and with a state without the territories and without settlements.”

Is that true? Hardly. Yes, there were attacks on Jews in 1920, 1921, 1936, and 1939. But these weren’t spontaneous outpourings of anti-Semitism; they were responses to Jewish immigration to Palestine—part of a cycle of violence, land expropriation, and ill will between the existing Arab residents of Palestine and the new Jewish ones.

That’s why Netanyahu’s aside is so important, because it reveals a whole fantastic worldview that underlies the day-to-day policies of his government—just like Yasser Arafat’s and Mahmood Abbas’s past denials of the scope of the Holocaust and of Jewish claims to the Temple Mount revealed their own.

On both sides, rejectionist nationalism is blind to historical reality, preferring a mythic struggle between good and evil. The evil Arabs hate the good Jews. The evil Jews steal the good Arabs’ land. Simple.

Did the Mufti of Jerusalem love the Jews? No. The ADL’s Greenblatt is right to call him a “virulent anti-Semite.” Would he have been happy to have seen them exterminated on European soil? Most likely, especially since the alternative was, in part, their emigration to Palestine.

But the notion that he originated the Final Solution is insane. It’s a convenient untruth that millions of Israeli voters believe, but that is usually kept from public view.

Except when it slips out by mistake.

—with additional reporting by Katie Zavadski