Earlier this week, when New York Times columnist Bret Stephens sent an outraged email to a university professor and provost over a tweet comparing him to a bedbug, critics said he had made a mountain out of a molehill.

A tweet that began with nine likes (and not a single retweet) blew up online. The professor said Stephens was trying to intimidate him over a harmless joke. Stephens deactivated his Twitter account but dug in during an MSNBC appearance, calling George Washington University professor David Karpf’s tweet “dehumanizing and totally unacceptable.”

Karpf thought the media circus was over by Friday. Then, the New York Times published a column by Stephens that, to many, seemed to compare Karpf’s bedbug comment to Nazis’ persecution of Jews during the Holocaust — sparking a new round of ridicule and prompting commenters to marvel at Stephens’s ability to keep his name in the headlines.

“So the Internet has been spending the entire week having good fun at [Stephens’s] expense, because he was taking himself way too seriously,” Karpf told The Washington Post on Saturday. “And then he had to find a way to take himself that much more seriously, by using his column space in the New York Times to call me, a Jew, a Nazi.”

Accompanied by a headline that reads “World War II and the Ingredients of Slaughter” and headed by a photo of Nazi propaganda minister Joseph Goebbels, the column describes a modern-day resurgence of the kind of dehumanizing rhetoric the Nazis deployed against the Jews they sought to exterminate. Stephens does not name Karpf, but he compares Twitter to the young radio technology that broadcast hate in the 1930s and highlights language comparing Jews with despised insects, including bedbugs.

Karpf said the implication that his tweet is comparable to anti-Semitic denigration of Jews “doesn’t seem like a proportionate response.”

“It takes what all week has been a light, entertaining and funny story and crosses a line,” he said.

Others reacted with similar disbelief, calling the apparent Nazi comparison inappropriate. One writer at Rolling Stone went so far as to say the piece should be retracted.

“Children shouldn’t have @nytimes columns,” Jamil Smith wrote.

And some homed in on a hyperlink in Stephens’s column that the Times removed Friday and said was “added by editors before publication to give readers a reference.” The link led to a Google Books search for the phrase “Jews as bedbugs” in a volume that one critic pointed out did not have any reviews on the site.

The New York Times did not immediately respond to a request for comment.

The controversy began earlier this week after reports of a bedbug infestation at the Times. Karpf, an activist and former Sierra Club board member who says he has been particularly disappointed with Stephens’s takes on climate change, made a joke about the conservative writer, whose columns have prompted some dismayed readers to cancel subscriptions.

“The bedbugs are a metaphor,” Karpf tweeted Monday. “The bedbugs are Bret Stephens.”

“He tends to write pretty lightweight, poorly researched columns about things that I know something about,” Karpf explained later. “So I’ve always seen him as this person that everyone complains about but we just can’t get rid of. He’s a bedbug.”

The tweet seemed destined for obscurity. (Karpf did not tag Stephens’s now-defunct Twitter handle.) But then Stephens emailed Karpf and copied George Washington University’s provost. He invited the professor to come to his home, meet his family and call him a bedbug in person in an act that “would take some genuine courage and intellectual integrity on your [Karpf’s] part.”

“I’m often amazed about the things supposedly decent people are prepared to say about other people — people they’ve never met — on Twitter,” Stephens wrote. “I think you’ve set a new standard.”

Stephens’s response went viral as critics called it an overreaction. Karpf and others pointed to far more demeaning insults frequently aimed at other writers, especially women and people of color.

Stephens, who did not immediately respond to questions from The Post on Saturday, told the paper earlier this week that his email to Karpf “speaks for itself.” In an interview with MSNBC, he insisted he was not trying to land Karpf in hot water by copying his boss on the email. He also referenced a history of “totalitarian regimes” comparing people with insects.

Stephens’s column published online Friday evening ignited a new wave of criticism by wading further into those historical comparisons.

“Anti-Semitism is exactly the same as delousing,” Stephens quotes Nazi leader Heinrich Himmler in his piece. Another statement he cites from an anti-Semite watching a ghetto burn makes the implied connection to Karpf’s tweet more explicit: “The bedbugs are on fire. The Germans are doing a great job.”

Stephens writes that “the rhetoric of infestation is back,” pointing to President Trump and other leaders’ descriptions of migrants. But he says the problem exists across the political spectrum.

“More of this talk will surely follow, and not just from the right,” Stephens writes. “The American left has become especially promiscuous when it comes to speaking pejoratively about entire categories of disfavored people.”

He goes on to describe the “unpopular political figures of our day” as “the moderate conservative, the skeptical liberal, the centrist wobbler” — a position Stephens occupies as a conservative alienated by Trump whose positions have drawn fire from both the left and right.

Criticism of Stephens’s response to the bedbugs tweet has come from both the right and the left.

Former Trump White House spokesman Sean Spicer, no stranger to online ridicule, laughed at Stephens’s indignation with conservative talk show host Sean Hannity, saying, “I think if that’s the worst thing that he’s been called, my goodness, take a look at my Twitter feed any day.”

“These guys can’t take a punch,” he said.

Some have defended Stephens. Letters published Saturday in the Los Angeles Times were critical of “name-calling” by Karpf, who detailed his takeaways from the spat with Stephens in the Times earlier this week.

Karpf wrote in that piece that he thinks he has received “remarkably little online abuse” stemming from the exchange with Stephens because he is a white man.

“If Stephens had directed his message to one of my female colleagues,” he wrote, “they would have faced much more online vitriol. … Many women with a public platform receive a death threat with their daily morning coffee.”

That reality, Karpf told The Post, has made Stephens’s decision to amplify his bedbug tweet all the more baffling. By the end of this week, the professor’s Twitter feed was returning to normal. The media requests were thinning. The smart thing for Stephens to do, he said, would have been to let the dust-up die — a lesson he discussed earlier this week with students of his class on political communications.

“It should have ended there,” Karpf said. “And then he decided he wanted to dunk on himself again."

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