Take Dylann Roof, who murdered nine black churchgoers in Charleston, South Carolina, after a chain of events that started with a simple Google search.

As Roof wrote in an online manifesto, when he typed the words “black on White crime” into Google he came across the website of a crudely racist group called the Council of Conservative Citizens . There, he found what he described as “pages upon pages of these brutal black on White murders.”

“I was in disbelief,” he wrote. “How could the news be blowing up the Trayvon Martin case while hundreds of these black on White murders got ignored?”

Since we exposed the problems with Google’s algorithm, which frequently served up misinformation, the search engine has cleaned up its results. But Roof is not the only one to fall for white supremacist propaganda. And the Council of Conservative Citizens isn’t the only one to disseminate it.

No less than the president of the United States tweeted a white nationalist talking point late Wednesday night, just hours after it was the subject of a report on Fox News.

President Trump’s tweet that South Africa is taking white farmers’ land ignores the country’s complicated and painful history of apartheid, and it constitutes at least the third brush with white nationalism his administration has had in just the last week.

There was the news Monday that his top economic adviser, Larry Kudlow, hosted the well-known white nationalist Peter Brimelow at his home, and the firing the previous Friday of his speechwriter, Darren Beattie, in the wake of revelations that Beattie had spoken at a conference attended by white nationalists.

Brimelow is one of the leading voices in the anti-immigrant movement and unabashedly argues that the United States should have immigration quotas that allow mostly white people in the country. His website VDARE, listed as a hate group by the SPLC, publishes the writings of racists and anti-Semites – some in academia – and helps provide a gloss of intellectualism to white nationalist propaganda. Trump’s top immigration adviser, Stephen Miller, is a Brimelow fan – at least he was in college, when he invited him to speak at his campus.

As our Intelligence Project director, Heidi Beirich, said earlier this week, “The highest office in our nation should not boast a single person associated with white nationalism, let alone several.”

But the same could be said of our nation’s ostensibly “lower” offices — the press — and of the ideas to which they give a platform.

We called on CNN several years ago to remove Lou Dobbs from the air after he spent years spreading racist conspiracy theories and blatant falsehoods about immigrants.

Dobbs’ claim in 2005 that an “invasion of illegal aliens” had brought 7,000 new cases of leprosy to the United States was as patently false as his 2003 claim that “illegal aliens” were “taking up a third of the cells in our federal penitentiaries.”

Yet Dobbs spent 29 years with CNN before finally leaving the network in 2009 and launching a show a year later at Fox News — the same network where Tucker Carlson aired a segment Wednesday night on white South African farmers.

In a world in which white nationalist talking points circulate with shocking ease, even seemingly benign stories must tread carefully. Last month a Washington Post story, for example, sparked widespread criticism for profiling Pennsylvania factory worker Heaven Engle, a white woman described as the lone English-speaker in the chicken plant where she worked, without once quoting her Latino coworkers.

For many critics, the story’s biggest red flag was its author’s description of population shifts “that will, with little historic precedent, reconfigure the racial and ethnic geography of an entire country” — an assertion that the Washington Post’s own Writers Group columnist Esther Cepeda told the Columbia Journalism Review conjures an argument used by white supremacists “when they’re getting their troops to rally that immigration must be stopped.”

White nationalism is no longer solely the purview of extremist circles. It has seeped into the mainstream media and even into the rhetoric of our country’s leadership — and it will take all of us to excise it.

The Editors.

P.S. Here are other pieces we think are valuable this week:

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