The evidence comes from psychology professor Jonathan Haidt, referenced in an article from Quillette which is linked and quoted following the re-post, and is worth reading in full.
In 2015, Haidt started Heterodox Academy in order to promote Viewpoint Diversity in the Academy.
In the following when I use the word Liberal with a capital "L," I mean Progressives, as very distinct from classical liberals. It is unfortunate that Progressives hijacked the word liberal. That might have been their last actual idea. It has forced us to say "classical liberal" in general conversation so as to be understood.
Also, the author to whom I was reacting used "liberal," and explaining why she was wrong would have lengthened an already longish post. Not to mention attempting to decode her point that Liberals aren't left, using 3 or 4 different terms.
Liberal Ayn Rand?
At Slate, Beverly Gage asks "Why Is There No Liberal Ayn Rand?"
Ask Republican vice presidential nominee Paul Ryan how he became a conservative and he’ll probably answer by citing a book. It might be Ayn Rand’s Atlas Shrugged. Or perhaps he’ll come up with Friedrich Hayek’s Road to Serfdom, or even Barry Goldwater’s Conscience of a Conservative. All of these books are staples of the modern conservative canon, works with the reputed power to radicalize even the most tepid Republican. Over the last half-century, they have been vital to the conservative movement’s success—and to liberalism’s demise.The answer to "Why Is There No Liberal Ayn Rand?" is right there, in the first sentence of the second paragraph. It's blindingly obvious (it's even Ms Gage's point) that "Liberals" don't think in terms of ideas. Ideas are hard work, intentions are easier. Liberals like to think in terms of intentions, and mostly they think in terms of how they interpret the intentions of others based on their own intentions to improve humanity. Liberals don't think like free people, they think in terms of how to apply power to the purpose of perfecting their fellows. To a Liberal, making everybody else perfect is what Liberty means...
We tend to think of the conservative influence in purely political terms: electing Ronald Reagan in 1980, picking away at Social Security, reducing taxes for the wealthy.
You might as well ask why there's no "Liberal" John Galt. A question you couldn't ask if you'd bothered to pay attention to certain compelling arguments from your opposition. Even if the ideas weren't compelling to you, would the demands of diversity not require you to attempt to understand? Would not a reasoned defense of your own ideas demand it?
And here the answer is again - in the first sentence of the third paragraph:
Liberals, by contrast, have been moving in the other direction over the last half-century, abandoning the idea that ideas can be powerful political tools. This may seem like a strange statement at a moment when American universities are widely understood to be bastions of liberalism, and when liberals themselves are often derided as eggheaded elites. But there is a difference between policy smarts honed in college classrooms and the kind of intellectual conversation that keeps a movement together. What conservatives have developed is what the left used to describe as a “movement culture”: a shared set of ideas and texts that bind activists together in common cause. Liberals, take note.But it's yet more subtle than that. First, the tea party people needed no institutional bastion of conservatism, controlled by an insular elite, to "re-educate" them. They'd have a hard time finding one if they did. They didn't need the ivory tower re-education camps in the first place. They get it innately. They fundamentally understand it. When they read Ayn Rand, they can see today's headlines. Our president's [then Obama] success as a community organizer doesn't make them swell with pride. Rather, it reminds them of Wesley Mouch.
"Liberals" have not abandoned the idea that ideas can be powerful political tools, they have abandoned the idea that anyone but them is allowed ideas. They are shocked, shocked when anyone deigns to challenge their intentions.
Liberals have channeled their energies even more narrowly over the past half-century, tending to prefer policy tweaks and electoral mapping to big-picture thinking. When was the last time you saw a prominent liberal politician ascribe his or her passion and interest in politics to, of all things, a book? The most dogged insistence on the influence of Obama’s early reading has come from his TeaParty critics, who fume constantly that he is about to carry out a secret plan laid out a half century ago by far-left writers ranging from Alinsky, the granddaddy of “community organizing,” to social reformer Frances Fox Piven.In fact, no. Tea party criticism is not about the books Obama may have read, it's about the books he "wrote."
Liberals may argue that they are better off knocking on doors and brainstorming policy than muddling through the great works of midcentury America.Policy without theory is untestable, and I can see why "Liberals" would consider that a strength. It allows them the excuse that without Obama's stimulus the unemployment rate he promised wouldn't go over 8%, but hit 10% (and more), deserves a Mulligan. He meant well.
And that Obama predicted the unemployment rate, with stimulus, would now be 5.6% is irrelevant. Get that? Not below 6%, but 5point6%. This is the same administration that quibbled over whether an unemployment rate of 8.254% should be reported as 8.3%.
So much for the precision wisdom of the centralized planners. You know, those very same people who turn out to be even more wrong than our president... in some book written by Ayn Rand...
And, finally, a note is required on the lead sentence of the closing paragraph:
In the current election this means that liberals also run the unnecessary risk of ceding intellectual authority to the right.Excuse me, but this is the risk Liberals continually choose. They do it gleefully, confident in the ascendance of their intentions, and with no thought about ideas. There is no necessary or unnecessary when peering down from the summit of moral superiority.
This election may represent increased risk for those who don't have, or care about, ideas; but they don't care enough to read Atlas Shrugged or Capitalism and Freedom to find out about the ideas that oppose them. Many of us who've read Atlas, have also read Das Kapital and Rules for Radicals and The Black Book of Communism. We have some idea what we're up against, and, unlike Ms Gage, we can even name Liberals we used to consider serious thinkers. We were wrong, but we could say why.
Liberals have largely lost the ability to respond to ideas. Ideas not their own make them angry. They have come to see ideas as the instruments by which they become victims. Ideas with which they disagree are, therefore, literally violence.
Now, I'd like to turn to professor Haidt as quoted at Quillette, for psychological research showing how Liberal disdain for ideas damages their ability to think. Not that they care: To them, it's a feature, not a bug.
The Psychology of Progressive Hostility"Liberals" don't think in terms of ideas. And worse than that, they've come to think in terms of stifling ideas. This makes them resistant to persuasion; which explains how they can claim skepticism about "climate change" is anti-science, while simultaneously denying there is any biological difference between men and women; describing science as racist; decrying rigor in engineering; and rejecting the theory of evolution.
In his remarkable book The Righteous Mind: Why Good People are Divided by Politics and Religion, [Jonathan] Haidt recalls a telling experiment. He and his colleagues Brian Nosek and Jesse Graham sought to discover how well conservative and what Haidt terms ‘liberal’ (ie: progressive) students understood one another by having them answer moral questions as they thought their political opponents would answer them. “The results were clear and consistent,” remarks Haidt. “In all analyses, conservatives were more accurate than liberals.” Asked to think the way a liberal thinks, conservatives answered moral questions just as the liberal would answer them, but liberal students were unable to do the reverse. Rather, they seemed to put moral ideas into the mouths of conservatives that they don’t hold. To put it bluntly, Haidt and his colleagues found that progressives don’t understand conservatives the way conservatives understand progressives. This he calls the ‘conservative advantage,’ and it goes a long way in explaining the different ways each side deals with opinions unlike their own. People get angry at what they don’t understand, and an all-progressive education ensures that they don’t understand.
Haidt’s research echoes arguments made by Thomas Sowell in A Conflict of Visions and Steven Pinker in The Blank Slate. Both Sowell and Pinker contend that conservatives see an unfortunate world of moral trade-offs in which every moral judgment comes with costs that must be properly balanced. Progressives, on the other hand, seem to be blind to, or in denial about, these trade-offs, whether economic and social; theirs is a utopian or unconstrained vision, in which every moral grievance must be immediately extinguished until we have perfected society. This is why conservatives don’t tend to express the same emotional hostility as the Left; a deeper grasp of the world’s complexity has the effect of encouraging intellectual humility. The conservative hears the progressive’s latest demands and says, “I can see how you might come to that conclusion, but I think you’ve overlooked the following…” In contrast, the progressive hears the conservative and thinks, “I have no idea why you would believe that. You’re probably a racist.”
It's all intentional, if devoid of actual ideas.