Jonathan Haidt, an author, psychologist, and professor of ethical leadership at New York University’s Stern School of Business, has been speaking out against this alarming trend. In 2015, he founded Heterodox Academy, a “politically diverse group of social scientists, natural scientists, humanists, and other scholars who want to improve our academic disciplines and universities.” His latest project, The Viewpoint Diversity Experience, “takes students on a six-step journey, at the end of which they will be better able to live alongside—and learn from—fellow students who do not share their politics.”

Haidt told me that this crackdown on ideological diversity is a recent phenomenon and is a result of the convergence of America’s political polarization, sorting (college campuses have finally reached a saturation point where there are virtually no conservative professors), and the rise of social media that “greatly amplifies the power of whatever the majority is.”

When students are no longer used to having their beliefs challenged, and orthodoxies can no longer be questioned. “Do you know why peanut allergies are rising? Because we haven’t exposed children to peanuts,” Haidt said recently on The Charlie Rose Show. People used to be forced to confront differing viewpoints. By sheltering them from uncomfortable ideas, we have essentially made them allergic to controversial ideas.