I was too young to have seen that at the time, but I have seen the footage. Vidal calls Buckley a “crypto-Nazi” to Buckley’s face, and the usually gentlemanly Buckley replied (after an anti-gay epithet which was less un-PC at that time), “stop calling me a crypto-Nazi or I will sock you in your goddamn face, and you will stay plastered.”
Vidal stopped.