This summer, Missouri Gov. Jay Nixon signed into law the Campus Free Expression Act, which prohibits the state’s universities from restricting student protests to designated “free speech zones.”

The law declares campuses a “traditional public forum” and guarantees students the right to express themselves freely on any outdoor space.

In recent weeks, as tensions mounted over a series of racial incidents in and around Mizzou, a group of student activists erected a tent city on Carnahan Quadrangle. So far, so good.

Then they planted a sign declaring their campsite a media-free zone.

So when their exercise of free speech caused the university president and chancellor to resign, the students sullied that victory by trying to chase reporters from that public forum. Yes, they’re a little unclear on the concept of the First Amendment.

There’s a lot of that going around. American universities, traditionally bastions of free speech, have taken a discouraging turn toward policing and even silencing forms of expression that might make students uncomfortable.

Last month at Yale, an intercultural affairs committee email cautioned students not to wear Halloween costumes that could be perceived as insensitive toward women, minorities, religious faiths or socioeconomic groups. (What’s left?)

The committee members had the right to raise those concerns. First Amendment, remember? But when a pair of administrators suggested the university shouldn’t tell people how to dress First Amendment again they were pilloried by students.

During an hourslong confrontation captured on video, one student argued that by pushing back against the Halloween police, the administrators failed to “create a place of comfort and home” for students. “It is not about creating an intellectual space!” the student shouted.

At UCLA, some students demanded that administrators punish partygoers who wore offensive costumes to a Kanye West-themed party hosted by campus Greek organizations.

Students have demanded that instructors be fired and commencement speakers be disinvited. They’ve filed Title IX gender discrimination complaints against professors over the content of their research. They’ve complained about buildings named after the rich white men who paid for them.

Shielding students from thoughts they might find objectionable is the opposite of what college is supposed to be about. But many universities have gone out of their way to accommodate those delicate sensibilities.

The University of California system has devoted months to educating its faculty on “microaggressions,” defined as “everyday verbal, nonverbal and environmental slights, snubs or insults, whether intentional or unintentional, that communicate hostile, derogatory or negative messages to target persons based solely upon their marginalized group membership.”

Those land mines include using the pronoun “he” in a gender-neutral context or mispronouncing non-English sounding names. Saying “America is the land of opportunity” suggests that those who don’t succeed are lazy. Asking a student “Where are you from?” suggests they aren’t a true American.

Some universities have directed instructors to correct (or report) each other for such utterances. Schools encourage students to report hurtful speech to online forums or even to campus police, who will forward the complaints to the administration for possible disciplinary action.

At some colleges, teachers are advised to alert students if an assignment contains provocative material that could trigger a strong emotional response. The lists of potential “triggers” goes beyond sexual and racial violence to include misogyny, classism and privilege. Some students have even complained about being traumatized by subject matter that wasn’t flagged with a “trigger warning.”

All of this creates an environment in which seemingly fragile young adults are allowed and enabled to avoid troubling thoughts, and the people who are supposed to be educating those students are required to second-guess their every word. Four years of that will do nothing to prepare students to run the world.

Freshman orientation should include an all-purpose trigger warning: This curriculum may contain material that some may consider racist, sexist, genderphobic, graphic, tasteless, politically incorrect or otherwise offensive. You can handle it.

Students are supposed to come to college to be exposed to challenging ideas, not be protected from them.