The anti-free speech takeover is so complete that now the fear of stirring a protest can determine what ideas students will hear.

Manhattan Institute Senior Fellow Jason Riley on his personal experience with liberal intolerance on campus.

By JASON L. RILEY

May 3, 2016 6:16 p.m. ET Wall Street Journal

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‘Progressives rule higher education,” write political scientists Jon Shields and Joshua Dunn Sr. in “Passing on the Right,” a new book on the dearth of conservative professors. “Their rule is not absolute. But conservatives are scarcer in academia than in just about any other major profession.”

Profs. Shields and Dunn aren’t exaggerating. In the humanities and social sciences, they note, surveys show that the percentage of self-described Marxist professors is around 18%, or nearly double that of self-described Republicans.

Nor is it merely classroom instruction that leftists tend to control. Liberal faculty and college administrators also closely monitor outside speakers invited to campus. The message conveyed to students is that people who challenge liberal dogma are not very welcome. A 2010 report by the Association of American Colleges and Universities found that only 40% of college freshman “strongly agreed that it is safe to hold unpopular positions on campus” and that by senior year it’s down to 30%.

In more recent years the intimidation has not only continued but intensified. A lecture on crime prevention by former New York City Police Commissioner Ray Kelly was canceled after Brown University students booed him off the stage. Scripps College in California invited and then disinvited Washington Post columnist George Will for criticizing ever-expanding definitions of criminal assault.

Planned commencement addresses by former Secretary of State Condoleezza Rice (Rutgers University), human-rights activist Ayaan Hirsi Ali (Brandeis University) and International Monetary Fund head Christine Lagarde (Smith College) were scuttled by faculty and student protesters, who cited Ms. Rice’s role in the Iraq war, Ms. Ali’s criticism of radical Islam and the IMF’s rules for lending countries money.

Yet you don’t have to be in such distinguished company to earn the ire of the campus left. Last month I was invited by a professor to speak at Virginia Tech in the fall. Last week, the same professor reluctantly rescinded the invitation, citing concerns from his department head and other faculty members that my writings on race in The Wall Street Journal would spark protests. Profiles in campus courage.

I have been writing about racial and various other issues in the Journal for more than two decades and lecturing at colleges for almost as long. I give around 15 campus speeches a year, and the venues vary: public schools, private institutions, liberal arts colleges, historically black schools, community colleges and graduate schools. Typically, I’m invited to offer an alternative perspective on an issue—to expose students to a way of thinking that they are unlikely to experience from, say, the 25% of sociology professors who also happen to identify as Marxists. The topics have ranged from politics to immigration to education and economics. Sometimes, I’ll debate a local professor. Other times, I simply speak and then take questions.

The Obama presidency, high-profile police shootings, the rise of the Black Lives Matter movement and the national debate surrounding mass incarceration have led to more invitations from schools to offer my opinion on race relations. Many of the students I encounter tend to believe that white racism largely explains racial disparities in the U.S. I encourage them to consider other possible explanations given black history. Large parts of these speeches are devoted to what was happening in black America in the first half of the 20th century with respect to employment, schooling, crime and parenting and why so many positive black trends either slowed dramatically or reversed course beginning in the 1960s.

Students who disagree with my lectures don’t hesitate to speak out during the Q&A. The back-and-forth is spirited but civil, and I have never been shouted down or physically threatened.

Still, a disinvitation at some point may have been inevitable. The Foundation for Individual Rights in Education (FIRE), which fights campus censorship, has compiled a “disinvitation database” that dates to 2000 and today includes nearly 300 incidents. According to FIRE, the “number of ‘disinvitation incidents’—i.e., efforts to prevent invited speakers from conveying their message on campus—has risen dramatically.”

I’ve lost count of the times I’ve been approached by conservative students after a lecture to a mostly liberal audience and thanked, almost surreptitiously, for coming to speak. They often offer an explanation for their relative silence during question periods when liberal students and faculty are firing away. “Being too outspoken would just make it more difficult,” a Wellesley student once told me. “You get to leave when you’re done. We have to live with these people until we graduate.”

In April, I spoke at the University of North Carolina at Chapel Hill, where the college Republicans who invited me took the precaution of clearing my name with liberal student groups “to make sure they wouldn’t be upset.”

We’ve reached a point where conservatives must have their campus speakers preapproved by left-wing pressure groups. If progressives aren’t already in absolute control of academia, they’re pretty close.

Mr. Riley, a Manhattan Institute senior fellow and Journal contributor, is the author of “Please Stop Helping Us: How Liberals Make It Harder for Blacks to Succeed” (Encounter Books, 2014).