Six months ago, the conservative radio host and blogger Erick Erickson wrote an opinion piece in the New York Times, inspiringly titled “How to Find Common Ground.”

“We owe it to one another to disagree agreeably, without anger or intimidation,” he wrote, noting that social media has put us all in polarized bubbles.

“A little more grace among us would go a long way toward healing the nation.”

Erickson is one of many who hasn’t done a great job of taking that advice since the massacre of 17 students and school staffers at Marjory Stoneman Douglas High School last month in Parkland, Fla.

“David Hogg Is A High School Bully,” was the headline of a blog post Erickson wrote soon after the shooting, referring to one of the student survivors who has become a leader in pushing for gun-control legislation. He didn’t mean Hogg was looting the lockers of his schoolmates, but, as the sub-headline claimed, “He is using his status as victim to inappropriately and ridiculously attack people while going unchallenged.”

Conspiracy theorists have questioned the credibility of the Parkland shooting survivors. This is how the theories entered the mainstream. (Elyse Samuels/The Washington Post)

This week, Erickson made it worse: He tweeted to his mass following what turned out to be an utter falsehood, based on an article on the RedState website speculating that Hogg may not have even been at school the day of the shooting.

He urged his audience to believe it, writing this “isn’t a fake news Gateway Pundit story.”

When that report was thoroughly debunked and RedState recanted, Erickson deleted his original tweet and posted an “update.” He did not apologize.

Emma González is a survivor of the Parkland shooting and a leader of the movement against gun violence. She has also become a target in far-right circles. (Elyse Samuels/The Washington Post)

“I spread misinformation from someone that was credible,” Erickson told me by phone, praising the reporting of RedState writer Sarah Rumpf.

“But I didn’t double down on it, and that’s the difference between someone responsible and someone who’s not responsible.”

Erickson stands by his harsh criticism of Hogg and others.

“I do think David Hogg has been a bully,” he told me, particularly in claiming that the National Rifle Association’s leadership has “blood splattered all over their faces” and in criticizing in strong language the NRA’s spokeswoman, “my friend Dana Loesch.”

The traditional media “is willfully helping” the students in their efforts to get new gun-control laws enacted, he said, so his kind of pushback is necessary.

When I asked him whether teenagers who have been through a school massacre and are rightfully outraged might deserve kinder treatment, he responded, “I think they deserve sympathy and respect, but not a free pass.”

Erickson’s actions matter because, despite his often extreme views, he’s seen as relatively moderate — someone who gets to offer platitudes about “healing” in the New York Times and whose comments get picked up — not as if they were the ravings of an Alex Jones, but as if he were a legitimate conservative opinion maker.

To wit: After the Hogg-as-bully post, the Hill — which focuses its news coverage on Congress — wrote up Erickson’s views as credulously as if they had been handed down on stone tablets.

What we’re seeing here is a spreading stain, in which conspiracy mongering from the likes of Infowars and, yes, Gateway Pundit is adopted by some elements of the formerly mainstream right and peddled to a receptive audience softened up for decades by Fox News.

That kind of thing can happen on the extreme left, too, but not as regularly and not as virulently. (And it’s a truism that corrections and “updates” everywhere fail to get the visibility of the original misinformation.)

There seems to be no floor of indecency that we agree to stay above.

As Charlie Warzel, who covers “information wars” for BuzzFeed News, put it recently: Extreme partisanship — pro-Trump media as well as parts of the far left — “is not about intellectual courage. It’s about winning.”

I spoke to Hogg about the attacks on him and other Stoneman Douglas students.

Still in Washington after last weekend’s March for Our Lives, the 17-year-old complained that “my mom is making me take a forced vacation.”

In recent days, he has been accused of giving a Nazi salute after his speech — he didn’t — just as his schoolmate Emma González was depicted as tearing up the Constitution. (She didn’t.)

“It’s just really sad,” Hogg said. “We’re so polarized as a nation. It’s so much easier to hate each other.”

The Nazi salute “is just stupid. It doesn’t deserve a response.”

But when people want to discuss policy, he’s willing to explain his point of view. Although the Stoneman Douglas students are often portrayed, he said, as wanting to take away everyone’s guns, most of them favor common-sense restrictions that respect the Second Amendment.

He added, “People need to realize when they counter these things to come with an American tone, not a divisive one.”

Admirable words. The problem is, the “American tone,” mostly on the right, has become a howling partisan shriek.

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