According to civil libertarians, conservatives and centrist liberals, American higher education has been hijacked by radical left-wing students who refuse to hear opposing viewpoints.
They point to students who shout down scholars over politically incorrect arguments, such as the protest this month against philosopher Christina Hoff Sommers, a critic of feminism, at Lewis and Clark Law School, and the physical attack on political scientist Charles Murray, co-author of the incendiary book The Bell Curve, when he spoke at Middlebury College last year.
As Mr David French complained in National Review: "Intolerance in the name of tolerance is the norm." Campus intolerance is a problem for the free exchange of ideas. But the fundamental cause isn't students' extreme leftism or any other political ideology.
It is a market-driven decision by universities, made decades ago, to treat students as consumers - they pay up to US$60,000 (S$79,000) per year for courses, excellent cuisine, comfortable accommodations and a lively campus life.
"Top colleges vie for students by offering amenities superior to those of the competition - better-stocked coffee bars in the library, better-equipped fitness centres in the dorms," lamented the literary scholar Andrew Delbanco in 2012.
Even at public universities, 18-year-olds are purchasing what is essentially a luxury product. Is it any wonder they feel entitled to control the experience?
The consumerisation of campus life started in the late 19th century, when reformers began to rethink higher education. Until the Civil War, colleges were focused on delivering what we today call a liberal education. Influenced by the spirit of Renaissance humanism, they offered a fixed curriculum, because educators believed that exposure to specific texts could perfect human beings: By reading about ancient Roman heroes in masterworks of Latin literature, Petrarch argued, a man would strengthen his soul and improve his character. Critics of antebellum American colleges rightly contended that this curriculum was too narrow.
But, in one crucial respect, they settled on a cure that was worse than the disease. Enamoured of laissez-faire economics, they replaced the old classical course of studies with a free-market approach to education.
Charles W. Eliot, as president of Harvard University from 1869 to 1909, proved to be the most influential of these advocates for the free-elective system. He advertised his philosophy with Darwinian vocabulary. "In education, as elsewhere," Eliot wrote in 1884, "it is the fittest that survives".
Undergraduates would now serve as the judges of the academic disciplines; those subjects that failed to win student attention would die. From vessels in need of moral improvement, American undergraduates transformed into capitalist consumers.
Despite pockets of resistance - most universities still have some distributional requirements, and a handful of "core curriculum" schools still exist, such as the University of Chicago and St John's College - Eliot's approach now dominates American higher education.
At almost all US colleges, the emphasis is on free choice, and students pick their courses in the same way they shop for jeans. They manage their own experience; they dictate its terms. It was inevitable that their expectation of control would seep outwards from academics into the rest of campus life.
By the turn of the 20th century, historian Frederick Rudolph informs us, undergraduates were using their newfound freedom to pick the easiest courses and direct their attentions to student life. A mania for college sports ensued, compelling Yale in 1914 to open the country's largest athletic arena, with a capacity of 70,000. This push to please the customer is accelerating.
"American colleges are spending a declining share of their budgets on instruction and more on administration and recreational facilities for students," The New York Times reported in 2010.
According to the American Institutes for Research's 2016 Delta Cost Project, from 2003 to 2013, public research universities in the United States boosted spending on student services by 22.3 per cent - a much steeper increase than the 9.5 per cent for research or the 9.4 per cent for instruction.
Undergraduates are acting accordingly: In 2013, the National Bureau of Economic Research released an important paper, "College as Country Club", which found a broad-based taste for amenities, rather than academic quality, on the part of American students. Professor Christopher Newfield, a prominent critic of what many label the "neoliberal university", has noted with alarm "the transformation of most student centres into midprice shopping malls."
And Professor Harry R. Lewis, a computer scientist who once served as the dean of Harvard College, described a strategy in his 2006 book, Excellence Without A Soul, that brings us closer to the roots of intolerance. "The problem with focusing on physical amenities, on parties and on which bands come to concerts on campus," he wrote, "is that doing so validates students' myopia." In other words, it teaches students that being educated matters less than being entertained.
Students, accustomed to authoring every facet of their college experience, now want their institutions to mirror their views. If the customers can determine the curriculum and select all their desired amenities, it stands to reason that they should also determine which speakers ought to be invited to campus and what opinions can be articulated in their midst. For today's students, one might say, speakers are amenities.
What's more, the drive to blacklist certain views isn't unique to the left. A student Republican club at Orange Coast College in California recently campaigned for its school to punish a professor who had labelled President Donald Trump a "white supremacist". Some religious students at Duke University boycotted the institution's summer reading list in 2015 because it contained a graphic novel that was forthright about gay romance. Although such examples of conservative student high jinks typically draw less attention, they hint at the existence of a less-ideologically-inspired climate of intolerance, fed by students who think they know best.
And these students think this for a good reason: Their schools, having given up any coherent vision of what it means to be an educated person, treat them this way.
All this suggests that blame for the troubled climate on many American college campuses cannot be laid solely at the feet of particular political movements. A well-articulated rationale for higher education, without all the tony amenities, would engender the vibrant intellectual community that critics find wanting today. That rationale should not encourage us to resurrect outdated curricula of the past.
Instead, colleges should focus on developing a canon of masterworks appropriate for today's globalised world. If we continue to treat students primarily as customers, we'll never encourage in young adults the sense of humility and seriousness of purpose requisite for learning - or for tolerating dissent.
• Eric Adler, an associate professor of classics at the University of Maryland at College Park, is the author of Classics, The Culture Wars, And Beyond.