National Review has a fraught relationship with National Socialism. In recent years, the magazine has taken to likening liberals and socialists to fascists and Nazis. In a much-derided article published last week, correspondent Kevin Williamson claimed that Senator Bernie Sanders is leading “a national-socialist movement, which is a queasy and uncomfortable thing to write about a man who is the son of Jewish immigrants from Poland and whose family was largely wiped out in the Holocaust.” Later in the article, Williamson added that Sanders is not a “national socialist in the mode of Alfred Rosenberg or Julius Streicher,” but this proviso couldn’t undo the implication that Sanders and his supporters are modern day Hitlerites. Nor is Williamson alone: His National Review colleague Jonah Goldberg authored a lengthy tome in 2008, Liberal Fascism, making essentially the same argument about the supposed links between modern day progressives and the early 20th century European far right.

While self-evidently absurd as a line of argument, the Williamson/Goldberg thesis is a fine example of projection, especially interesting because of their magazine’s long history of both publishing pro-fascist arguments and also resenting any accusations of being pro-Nazi. As the new documentary The Best of Enemies reminds us, the relationship between National Review and Nazism was once the stuff of national television drama in a notorious debate between Gore Vidal and National Review founder William F. Buckley. In August 1968, during the Democratic Convention in Chicago, Buckley compared New Left youths carrying pro–Viet Cong flags to pro-Nazis. Vidal responded by saying, “As far as I’m concerned, the only sort of pro- or crypto-Nazi that I can think of is yourself.” This set off Buckley, who went bugged eyed and threatened Vidal, saying, “Now listen, you queer, stop calling me a crypto-Nazi or I’ll sock you in the goddamn face.”

Best of Enemies does a fine job of recreating the Vidal/Buckley clash as a TV spectacle, but doesn’t really adequately explain why Buckley—who was a veteran debater and kept his cool in heated exchanges with adversaries like Noam Chomsky and John Kenneth Galbraith, who were just as formidable as Vidal—became unhinged at that particular moment. A better explanation can be found in the history of National Review itself.

As John Judis documents in his 1988 biography of Buckley, the conservative pundit’s father and namesake, William F. Buckley Sr., was an anti-Semite and fascist sympathizer who tried his best to pass along his ideas to his large brood. In 1937, four of the Buckley kids burned a cross outside a Jewish resort. The eleven-year-old William Buckley Jr. didn’t participate in the cross burning but only because he was deemed too young to participate and by his own account “wept tears of frustration” at being left out of the hate crime. At this point the young Buckley agreed with his father’s worldview, and would argue, in the words of a childhood friend, that “Bolshevik Russia was an infinitely greater threat than Nazi Germany.” The Spanish fascist leader Francisco Franco was a hero in the Buckley household, celebrated as a bulwark against the red menace.

As he came into adulthood Buckley gradually outgrew the anti-Semitism of his father. While the young Buckley did intervene to break up the engagement between his Jewish friend Tom Guinzburg and his sister Jane, he also came to see political anti-Semitism as toxic. After forming National Review in 1955, Buckley’s relationship to the European right was complicated: He continued to admire Franco as a hero but drew a distinction between fascism (permissible) and outright Nazism (beyond the pale). National Review worked hard to distance itself from openly anti-Semitic publications: In 1958 Buckley circulated a memo declaring that no one who served on the masthead of The American Mercury could also serve on the masthead of National Review.