Here’s the problem with suggesting that upsetting speech warrants “safe spaces,” or otherwise conflating mere words with physical assault: If speech is violence, then violence becomes a justifiable response to speech.

Just ask college students. A fifth of undergrads now say it’s acceptable to use physical force to silence a speaker who makes “offensive and hurtful statements.”

That’s one finding from a disturbing new survey of students conducted by John Villasenor, a Brookings Institution senior fellow and University of California at Los Angeles professor.

In August, motivated by concerns about the “narrowing window of permissible topics” for discussion on campuses, Villasenor conducted a nationwide survey of 1,500 undergraduate students at four-year colleges. Financial support for the survey was provided by the Charles Koch Foundation, which Villasenor said had no involvement in designing, administering or analyzing the questionnaire; as of this writing, the foundation had also not seen his results.