correction: An earlier version of this column misidentified the parent company of Fox News. It is 21st Century Fox. This version has been updated.

Columnist

After a “lone wolf” Islamist militant attack, the media invariably ask: What inspired him to kill? Usually the answer is found in Islamist militant propaganda. We need to ask the same question about right-wing terrorism. What inspired Cesar Sayoc to allegedly send mail bombs to prominent liberals? What inspired Robert Bowers to allegedly gun down 11 people in a Pittsburgh synagogue? What inspired Gregory Bush to allegedly kill two African Americans in Jeffersontown, Ky., after failing to enter a predominantly black church?

To ask these questions in no way obviates the perpetrators’ ultimate responsibility for the evil that they do. But terrorists do not operate in a vacuum. So who created the environment in which right-wing terrorism has become far more commonplace — and, since 9/11, far more deadly — than Islamist terrorism in America?

President Trump — by championing “nationalism,” denouncing “globalists” such as Jewish financier George Soros, vilifying immigrants as “snakes” and “animals,” fearmongering about a refugee caravan and defending white supremacists as “fine people” — bears a substantial share of the blame.

Some of his Republican followers are even more extreme. Rep. Matt Gaetz (R-Fla.) brought a Holocaust denier to the State of the Union and has blamed Soros for financing a Central American immigrant caravan. Rep. Steve King (R-Iowa) gave an interview to a far-right Austrian website in which he endorsed the white-supremacist claim that white nations are committing “slow-motion cultural suicide” by allowing in immigrants of color.

Even GOP leaders are joining in. House Majority Leader Kevin McCarthy (R-Calif.) posted and then deleted a tweet accusing Soros, Michael Bloomberg and Tom Steyer of buying the election. (Soros and Bloomberg are Jewish; Steyer is an Episcopalian whose father was Jewish.) Sen. Charles E. Grassley (R-Iowa), chairman of the Senate Judiciary Committee, blamed Soros for funding protests against then-Supreme Court nominee Brett M. Kavanaugh.

Where do these politicians get these noxious ideas? From a right-wing media industrial machine that includes Fox News, Breitbart, Infowars, Newsmax, the Daily Caller, Gateway Pundit and many other outlets. It was Maria Bartiromo of Fox Business Network who asked Grassley if Soros was behind the Kavanaugh protests — and after Grassley endorsed the charge, Trump gave it his imprimatur. The Wall Street Journal, in turn, ran an op-ed endorsing this calumny. Last week, Fox Business host Lou Dobbs interviewed Chris Farrell of Judicial Watch, who claimed that the Central American caravan was directed by the “Soros-occupied State Department,” echoing neo-Nazi propaganda about a “Zionist-occupied government.” (Fox Business has since apologized.)

Fox News isn’t just vilifying a major Jewish donor to liberal causes. It is also demonizing all Democrats — literally. Host Jeanine Pirro refers to them as “demon rats.”

This nonstop drumbeat of over-the-top invective and irrational conspiracy theories can drive otherwise sane conservatives to extremism — and it can drive those who were already unstable to violence. The New York Times reports that until 2016, Cesar Sayoc’s Facebook page was full of “decadent meals, gym workouts, scantily clad women and sports games. . . . But that year, Mr. Sayoc’s social media presence took on a darker and more partisan tone.” That’s when he began posting “stories from Infowars, World Net Daily, Breitbart and other right-wing websites,” which “showed a fascination with Islamist terrorism, illegal immigration and anti-Clinton conspiracy theories.”

Naturally, when Sayoc sent letter bombs to Trump’s critics, the right-wing media claimed it must be a “false flag” operation. Once the preserve of the paranoid radio host Alex Jones, this lunacy is now propagated by the likes of Ann Coulter, Rush Limbaugh, Dinesh D’Souza, Frank Gaffney, Donald Trump Jr. and Michael Savage. D’Souza tweeted: “Fake sexual assault victims. Fake refugees. Now fake mail bombs. We are all learning how the media left are masters of distortion, deflection & deception.” Trump himself appeared to give winking support to this crackpot theory by referring to “this ‘Bomb’ stuff.” Even after Sayoc’s arrest, few “false flag” theorists recanted or apologized.

There is partisanship on both sides of the political spectrum, but no left-wing outlets propagate extremism as successfully or widely as conservative media do. A new study of “Network Propaganda” by three Harvard researchers notes that liberals, by and large, get their news from sources such as The Post, the Times, NPR and CNN that, regardless of any political bias, also engage in rigorous fact-checking. Conservatives, by contrast, are being brainwashed by right-wing media that are an “echo chamber” for “rumor and conspiracy theory.”

The frightening thing is that the right-wing media will be here long after Trump and the current crop of Republican politicians are gone. These outlets have a First Amendment right to say what they want, but investors and advertisers also have a right to take their dollars elsewhere. If Rupert Murdoch and his sons won’t rein in its extremist propaganda, advertisers should flee Fox, and investors should flee its parent company, 21st Century Fox. Its stock should become as toxic as shares of mining companies that produce “blood diamonds.” The propagandists and politicians who are radicalizing the American right must not be allowed to escape responsibility for the dangerous consequences of their actions.