Jeffrey Lord appears at a rally for then-president-elect Donald Trump in Hershey, Pa., on Dec. 15, 2016. (Matt Rourke/AP) (Matt Rourke/AP)

CNN fired prominent commentator Jeffrey Lord on Thursday after he tweeted the Nazi salutation “Sieg Heil!” in response to a feud with a liberal activist.

“Nazi salutes are indefensible,” a CNN spokesperson said in a statement. “Jeffrey Lord is no longer with the network.”

Lord, a former official in the Reagan administration, has been featured on many CNN panels and has been a reliable defender of President Trump. He began working with the network during the presidential campaign, and has spoken on behalf of Trump since then.

[Margaret Sullivan: For fans of inane punditry, CNN’s double loss of Lord and McEnany is crushing]

His undoing was an outgrowth of a long-running argument between Lord and Angelo Carusone, the president of Media Matters for America, a liberal media watchdog group that has been critical of Lord.

(Peter Stevenson/The Washington Post)

In a column for the conservative American Spectator on Thursday, Lord called Carusone’s group the “Media Matters Fascists.” In a follow-up post, he called them “anti-free speech bigots who, in typical fascist style, make it their mission to shut down speech they don’t like.”

Lord was specifically critical of Media Matters’ promotion of an ad boycott against Fox News host Sean Hannity. Lord said Media Matters was playing a “fascist game” by targeting Hannity’s sponsors. The group has led other boycotts against conservative media figures, including Rush Limbaugh and Bill O’Reilly.

“This is America, Angelo. Not Fascist Italy, Nazi Germany or Communist Russia,” Lord wrote.

Lord referenced his column in a tweet aimed at Carusone, who tweeted back that Lord’s column incorrectly referred to his group as “MMF” (for “Media Matters Fascists.”)

Carusone asked, “Why do you expect anyone to take you seriously when you don’t take yourself seriously.”

Lord’s responded by tweeting back “Sieg Heil!,” a phrase used by Nazi-party members at political rallies. It means “hail victory” and is so closely associated with Adolf Hitler that its use is banned in Germany.

He deleted the tweet, but other users captured it before he did so.

The two men had traded barbs on Twitter earlier in the week over billionaire George Soros, who has donated funds to Media Matters in the past. In an earlier column, Lord had been critical of Soros’ contributions to the organization.

Carusone told Lord that one of his columns was “full of lies” and said “Soros gave us one donation one time . . . in 2010.”

CNN began employing pro-Trump commentators in 2015 to balance out its discussion of presidential politics and the candidates. Lord, who began at CNN soon after Trump declared his candidacy in June of that year, has been a prime-time regular, appearing on Anderson Cooper’s program and others.

He was often on the defensive during discussions of Trump’s actions or comments, and often used historical references to justify the president’s behavior.

Among his most famous exchanges was one with liberal CNN pundit Van Jones in March of last year over the history of the Ku Klux Klan.

CNN signed Lord to a year-long contract in December. It was supposed to run through the end of 2017.

Lord is the second Trump supporter to leave CNN in the past week. Kayleigh McEnany left the network to become the Republican National Committee’s spokeswoman. She also recently appeared in a video produced by Trump’s reelection committee.