What’s wrong with college students? That was the question again on everyone’s minds after last week’s episode at Vermont’s Middlebury College, where social-justice warriors ran scholar Charles Murray off campus. A left-wing Middlebury professor who thought Mr. Murray had the right to express his views was injured escaping the student mob. 

People across the political spectrum seem to agree on an explanation for what’s happening on campuses throughout the country: It’s “the bubble.”

In Boston Magazine, Sarah Lawrence College professor Samuel Abrams warned of the “tiny bubbles of liberalism” that tend to form at small liberal-arts schools. Berry College political scientist Peter Lawler wrote on National Review’s website that “our elite colleges—despite their official commitment to diversity—are pretty much all part of the bubble.” Middlebury students and faculty, Mr. Lawler added, could have benefited from Mr. Murray’s diagnosis of their bubble’s “distinctive prejudices.”

Some campus activists have criticized Middlebury for being a bubble of “white privilege.” In 2014, a student writing under the pseudonym “Princess of Color” complained about “the harsh lack of racial and socioeconomic diversity” at the school. Prior to Mr. Murray’s campus visit, another student alleged that Middlebury students and faculty were “comfortable living in a complicit bubble of racism” thanks to their “white fragility.”

Last year students at the college were required to take a seminar covering topics like inclusivity, identity, privilege and inequality. The purpose? To get them out of their bubbles.

Many liberal-arts colleges like Middlebury were established in remote locations or in small towns precisely to provide students with a respite from the “real world.” The traditional idea of the liberal-arts college was that it provided students with a temporary oasis from practical life, a period when they could immerse themselves in the great questions and develop a foundation for going forward in life. It was a “bubble,” but a useful one. 

Educators, parents and students once thought this was a good thing. Many academic leaders in the last century liked to cite Cardinal John Henry Newman. In “The Idea of a University” (1852), Newman wrote that it “is only after our physical and political needs are supplied, and when we are ‘free from necessary duties and cares,’ that we are in a condition for ‘desiring to see, to hear, and to learn.’ ” Many also recognized the tension between professional and liberal-arts education and worked to maintain the undergraduate college as a preserve for general education in the humanities. 

In 1936 University of Chicago chancellor Robert Maynard Hutchinswrote that a liberal education frees a person “from the prison-house of his class, race, time, place, background, family, and even his nation.” To gain such an education, students had to remove themselves from the daily grind of earning a living and attending to family responsibilities.

More recently, Allan Bloom restated this principle in “The Closing of the American Mind” (1987), where he wrote that a young person has four “charmed years” of freedom with which “to discover himself—a space between the intellectual wasteland he has left behind and the inevitable dreary professional training that awaits him after the baccalaureate.” Even as he wrote, Bloom recognized that this opportunity was being cast aside due to the intertwined pressures of specialization, professionalism and ideology—and now, expense and debt have further complicated the picture. 

The original rationale for the liberal-arts college has been displaced by the ideological impulses that fly under the banner of diversity, inclusion and equality. Colleges like Middlebury now wish to be “relevant” and on the cutting edge of social change, with the goal of redeeming American society from its exclusionary heritage. Many liberal-arts professors succumbed to this temptation in the 1960s. 

Today, ideological conformity has been institutionalized on the nation’s campuses. Students are encouraged to look upon American society from a perspective of righteous indignation. Anyone challenging the assumptions underlying this perspective risks provoking the kinds of confrontations seen at Middlebury, Berkeley and elsewhere. 

Because students at these schools operate in a bubble, they have little understanding of American society—and little sympathy for most Americans struggling to make a living. For a host of reasons, they are poorly equipped to engage in redemptive crusades of any kind. A genuine liberal-arts education would help them realize this. Without it, though, the “charmed years” will continue to look much less charming—both for the students and the society they will inherit. 

Mr. Piereson is president of the William E. Simon Foundation. Ms. Riley is a senior fellow at the Independent Women’s Forum.