For sheer chaos, nothing in my lifetime rivals 1968, with the assassinations of Rev. King and Robert Kennedy, followed by the Chicago police riot at the Democratic National Convention and the presidential candidacy of Alabama’s segregationist Gov. George Wallace.

One could go on. I’ve always been a fan of Philip Roth’s novel The Plot Against America, an alternate history in which Charles Lindbergh defeated FDR in the 1940 presidential election, leading to a Hitler-friendly regime.

Absurd, you say? Not much crazier than Donald Trump’s man-crush on Vladimir Putin. Not to mention North Korean dictator Kim Jong Un.

That said, there’s plenty of evidence for Haidt’s view of “social media as a universal solvent, breaking down bonds and weakening institutions everywhere it reached.” He thinks the great turning point came in 2009, when online platforms invented the “like,” “retweet” and “share” functions, greatly enhancing what George Orwell called “groupthink.”

Online echo chambers definitely encourage users to communicate only with like-minded people, Haidt stresses, thus “supercharging confirmation bias, making it far easier for people to find evidence for absurd beliefs and conspiracy theories ... such as those spreading across right-wing media and now into Congress. ‘Pizzagate,’ QAnon, the belief that vaccines contain microchips, the conviction that Donald Trump won re-election — it’s hard to imagine any of these ideas or belief systems reaching the levels that they have without Facebook and Twitter.”

True enough. On the Democratic left, Haidt thinks, online groupthink has helped stifle dissent at universities and large news organizations. One small but telling example: The New York Times has never published a review of J.K. Rowling’s most recent novel, The Ink Black Heart, although the author is perhaps the best-selling novelist in the English-speaking world. However, she has also expressed views deemed transphobic by activists and thus has been rendered an unperson in literary circles.

(I bought the novel on publication day but found it heavy going. I also find the hubbub over her views incomprehensible.)

The great political beneficiary of social media, Haidt argues, has been Trump, whom he calls “the first politician to master the new dynamics of the post-Babel era, in which outrage is the key to virality, stage performance crushes competence ...”

To me, Trump’s superpower was TV, not the internet. He imported the race-based themes of professional wrestling to politics; that, and his sheer shamelessness. Because something else happened in 2009 that was far more consequential to the MAGA crowd than Facebook’s “like” function: The United States inaugurated Barack Obama, a Black president with an Islamic-sounding name.

A large proportion of Trump’s target audience simply lost their minds. And social media had very little to do with it. One of his most attention-grabbing falsehoods, early on, was that he’d employed investigators who were making shocking discoveries about Obama’s allegedly foreign birth and secret Muslim faith. Un-American outsiders were taking over.

The same crowd that heeded Rev. Jerry Falwell’s Clinton Chronicles videos, depicting Bill and Hillary Clinton’s many supposed murders, and who sat stuck in traffic listening to Rush Limbaugh railing against liberal perfidy was all too ready to believe that a Black impostor had infiltrated the White House.

And then along came the Fox News network, developing a larger audience and a more comprehensively conspiratorial worldview — to the point where its executives now admit pandering to audience views not of what actually happened out there in the visible world, but what ought to have happened in the world of their collective imagination.

So it’s all Facebook’s fault?

I don’t think so.