CNN cut ties on Thursday with the conservative commentator Jeffrey Lord after he tweeted a Nazi salute at a critic. A network spokesperson confirmed that Lord was no longer with the network and said: “Nazi salutes are indefensible.”

The statement came hours after Lord tweeted the Nazi slogan “Sieg Heil!” at the head of a liberal advocacy group, Media Matters for America. Retained by CNN in August 2015, Lord was an indefatigable on-air supporter of Donald Trump throughout his candidacy and since his election.

A contributor to the conservative magazine the American Spectator, Lord is a former aide to Jack Kemp and Ronald Reagan. He had repeatedly clashed with Media Matters’ president, Angelo Carusone, whose group condemned CNN for employing him as a commentator.

Following a harsh exchange of tweets with Carusone earlier this week, Lord posted an article for the American Spectator on Thursday morning, calling Carusone’s group the “Media Matters Fascists” and casting them as “anti-free speech bigots who, in typical fascist style, make it their mission to shut down speech they don’t like”.

During the day the Twitter sparring resumed, with Lord finally responding to Carusone with the tweet: “Sieg Heil!” In subsequent tweets, he insisted he meant to be “mocking Nazis and Fascists”.

But refusing to back down to a firestorm, he posted: “Why would I delete something that mocks the Fascists at Media Matters Fascists?” His defiant tweet in his firing’s aftermath: “LOL!”

During his presence on CNN’s airwaves, Lord had frequently riled CNN hosts including Anderson Cooper and Don Lemon, fellow commentators and viewers with many of his statements.

During Super Tuesday election night coverage in March 2016, he argued that the KKK was a leftwing organization because of Democrats’ support of it many decades before. In April, he called Trump the “Martin Luther King” of healthcare. An email message sent to Lord was not immediately returned.