“Shanna, they bought their tickets, they knew what they were getting into. I say: let ’em crash!” The TV news comment in the 1980 movie Airplane! was, of course, inspired by America’s new strain of gladiatorial punditry and counter-punditry, introduced by ABC News’s pioneering 1968 convention debates between conservative William F Buckley Jr and liberal Gore Vidal – the subject of this documentary.

It is fascinating, not for any supposed lost standard of excellence in argument – the drawling debates look like a squabble between two snippy and indistinguishable twins – but for showing us two examples of that exquisite, extinct breed: the literate “political classes” willing to exchange high-flown badinage on television. The contest was always about who would lose their cool first and it was Buckley, furious at being called a “crypto-Nazi” and threatening to sock the “queer” Vidal in the face, live on camera. Buckley had, therefore, humiliatingly lost, but Vidal endured the ignominy of irrelevance as Buckley became the height of political fashion in the Reaganite years. They both then entered the wilderness as incorrect patrician wordsmiths who no one cared about any more.

In the US, now there is Fox News and – occupying less space – Jon Stewart’s Daily Show, political comment is compartmentalised; pundits don’t hate each other publicly the way Vidal and Buckley did. They are more concerned with their online fanbase and less willing to risk a TV disaster that would be career-definingly immortalised on YouTube. These debates are a fascinating, lost minuet of personal and political disdain.