The German magazine Der Spiegel last week fired Claas Relotius, one of its star reporters, for fabricating sources and details in at least 14 articles and perhaps as many as 55. There was an unmistakable thread tying together Relotius’ tall tales: seething anti-Americanism.

In his downfall, we see the crisis of left-liberal journalism in microcosm: Animosity toward Red America too often trumps reporting the facts — a blind spot that leads astray the prestige press on both sides of the Atlantic.

Relotius’ embellished stories could plausibly be collected in a book-length portrait of the ugliness and violence of American life — that is, if they were true.

There was his award-winning “The Last Witness,” about an American woman who volunteers to watch the execution of death-row inmates (he made the whole thing up). There was “Number 440,” which Der Spiegel described as “the gripping account of a Yemenite wrongly imprisoned in Guantanamo” (it contained multiple fabrications).

And then there was the article that got him busted: a “report” on American vigilantes guarding the US-Mexico border, complete with a hand-painted “Mexicans Keep Out” sign that didn’t exist.

Relotius was no small-time hack. He won CNN’s Journalist of the Year award in 2014 and last year made it to Forbes’ “30 Under 30” list for European media.

His anti-Americanism fit in nicely with Der Spiegel’s worldview. This is the same magazine, after all, that in May published an editorial ­announcing its “Resistance Against America.”

On Friday, US Ambassador to Germany ­Richard Grenell called for an independent investigation of anti-American bias at Der Spiegel. In a letter to the magazine’s editor-in-chief, Grenell wrote: “The fundamental question is how such blatant anti-Americanism could be published without an editor questioning its accuracy.”

The answer is simple. Saying bad things about middle Americans and conservatives is the surest way to safeguard your writing against close editorial scrutiny. Stories that advance a left-liberal worldview are often too good to fact-check. If it’s anti-American, or anti-conservative, it has to be true.

And if it’s not strictly factually true, then it’s thematically “true enough.” The key is to leave readers feeling disgusted by your enemy.

There were examples closer to home this year. The New York Times reported that Nikki Haley, America’s outgoing UN envoy, had spent tens of thousands of taxpayer dollars on curtains for her apartment in the Big Apple. But it turned out the Obama administration had purchased the fancy curtains.

The New Yorker ran a series of stories about a woman who accused ­Supreme Court nominee Brett Kavanaugh of sexual misconduct — without any corroborating evidence of an incident that supposedly took place in the early 1980s.

CNN fell hard for North Korean PR at the Winter Olympics. “If ‘diplomatic dance’ were an event at the Winter Olympics,” the network breathlessly claimed, “Kim Jong-un’s younger sister would be favored to win gold.”

If a mainstream journalist ever filed stories that weak, but with a conservative or pro-American bent, his reporting would be fact-checked out of existence; the articles mentioned above went viral.

Yes, Relotius is a special type of pathological fabulist who comes along only every few years. Americans might remember Stephen Glass, who got caught writing hoax stories at the New Republic in 1998, and Jayson Blair, who imploded spectacularly at the New York Times in 2003. Such writers seem to have a congenital need to push the bounds of reality until their careers self-destruct.

But Relotius is also an extreme representative of an ideologically driven press.

There’s been much talk about President Trump’s penchant for attacking the media. It’s true that his labeling the press “the enemy of the people” is dangerous. But activist journalists have harmed their profession far more than Trump ever could.

The Times Square Alliance recently announced that New Year’s Eve in Times Square will be an official celebration of journalism. It’s a fitting way for the left-liberal media to end the year, with the ceremonial dropping of the ball.

Abe Greenwald is senior editor of Commentary.