The gesture was small, but it contained multitudes.
At a raucous rally in Montana last week, a Trump supporter — juiced up by the president’s crude praise of a congressman who body-slammed a reporter — looked directly at CNN reporter Jim Acosta.
Then he ran his thumb across his throat. And laughed.
Later, Acosta described "the Trump effect."
"It has normalized and sanitized nastiness and cruelty in a way that I just never thought I would see," he said, shortly after that Montana rally.
The Trump effect is a straight line from years of his hateful rhetoric to real-world danger. It's a line that goes directly from disrespect to pipe bomb.
And — almost inevitably — it will eventually go from failed attempt to spilled blood.
If you can't see it, you aren't looking.
But on Wednesday, plenty of people weren't looking.
The news reports of bombs sent to the most frequent objects of President Donald Trump's sustained criticism brought a torrent of nonsense. This was a false-flag operation, some charged, instigated by Trump's enemies to bring sympathy.
Ann Coulter tweeted that bombs have been, throughout history, "a liberal tactic."
And radio behemoth Rush Limbaugh, as quoted in HuffPost, jumped in with his view that Republicans don't do this sort of thing, and a Democratic operative was the more likely culprit.
But let's get real. Everyone targeted by the pipe bombs had been the subject of endless hours of Fox News commentary. The list of targets read like Sean Hannity's pre-broadcast crib notes: Hillary Clinton, former President Barack Obama and former CIA chief John Brennan - and, as the representative of evil mainstream media, CNN.
As usual, Trump himself projected blame everywhere but where it belongs.
In what Katie Rogers and Eileen Sullivan of the New York Times described as the president's "rhetorical jujitsu," he combined swipes at the news media and Democrats with a call to "come together in peace and harmony."
And in a reprehensible Thursday morning tweet, Trump doubled down: "A very big part of the Anger we see today in our society is caused by the purposely false and inaccurate reporting of the Mainstream Media that I refer to as Fake News. ... Mainstream Media must clean up its act, FAST!"
There is no story now — even one about terrorist acts — that doesn’t devolve into the hyperpartisan blame game, led by the president.
In this case, placing the blame appropriately required nothing but common sense.
CNN boss Jeff Zucker got it right: "There is a total and complete lack of understanding at the White House about the seriousness of their continued attacks on the media. The President, and especially the White House Press Secretary, should understand their words matter. Thus far, they have shown no comprehension of that."
(That Zucker, both at NBC and at CNN, undoubtedly helped create Trump as president doesn't take away the truth of his statement. )
There's real danger in these assaults.
There's danger in "lock her up," in birtherism, in retaliating against former CIA director Brennan by revoking his security clearance. There's danger in calling reporters "the enemy of the people" and in celebrating Montana Congressman Greg Gianforte for roughing up Guardian reporter Ben Jacobs.
And the danger only grows. Last week, a Montana Republican official resigned her post after not only cheering Gianforte's body-slam but, in remarks on a radio show, taking it an ugly step further:
"If that kid had done to me what he did to Greg, I would have shot him," she said.
When a gunman shot and killed five employees of the Capital Gazette last summer in Annapolis, Maryland, it seemed wise not to tie the tragedy to Trump's anti-media assaults. After all, Jarrod Ramos had been harassing journalists at the small daily newspaper for years, carrying a grudge about coverage of him he found unfair.
Now I’m not so sure. Trump’s rhetoric makes the unthinkable seem possible. Worthy of a second thought — or more.
What I am certain of is that the danger that came from the top — from Trump — will worsen unless he does everything in his power to change.
To model, in words and actions, the peace and unity that he tepidly endorsed on Wednesday.
To recognize his own gargantuan role in the problem, to honestly confront "the Trump effect."
Of course, there's no reason to think that will happen.
And so — dreadful as it is to say — we know what will.
Margaret Sullivan is The Washington Post’s media columnist. Previously, she was the New York Times public editor, and the chief editor of the Buffalo News, her hometown paper. @sulliview