A documentary by Robert Gordon and Morgan Neville. Rated PG.

The concept of the public intellectual is now so obscure, it takes long-form documentaries to explain it. Best of Enemies has a fairly easy task, though.

Its dual subjects, both born to patrician families in 1925, loathed and mirrored each other with revealing passion. And they did that most visibly at a crossroads moment that, arguably, found the United States moving doggedly in the wrong direction.

The reptilian William F. Buckley remains fascinating, in part, because his cultured persona was seemingly at odds with his fascistic impulses. Through his National Review magazine and many TV appearances, he presaged a form of reactionary fantasy-think he himself later came to fear. A champion of right-wing crusader Joseph McCarthy and crackpot candidate Barry Goldwater, he also despised libertarian diva Ayn Rand and was (belatedly) vocal in his support of Martin Luther King Jr. and the legalization of marijuana.

Almost openly gay at a time when the closet was nearly windowless, Gore Vidal was such a prolific author, historian, and screenwriter (Ben-Hur and The Best Man, among many others) that when accused of being unpatriotic, he answered, “How can I be anti-American? I’m the country’s official biographer.” A relentless exposer of racism, fundamentalism, homophobia, anti-intellectualism, environmental degradation, and inter-class exploitation—in short, everything threatening us today—he nonetheless lived “in a personal cloud of outrageous leisure”, as dryly noted in one of many TV profiles excerpted in this expertly assembled documentary.

Directed by Robert Gordon and Morgan Neville, who previously focused on films about blues and soul musicians (like Twenty Feet From Stardom), the breezy effort examines 10 debates between these verbose heavyweights, televised by a struggling ABC during the Republican and Democratic conventions of 1968, near the peak of the Vietnam War.

The filmmakers argue persuasively, with some oversimplification, that the prolonged joust—culminating in a flash round of personal insults that deeply wounded both men—was a final watershed of public debate and a harbinger of what we’d get in its place: paid pundits, usually wrong, screaming at each other about things that have already been decided.