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 it.

Villasenor's questions were designed to gauge students' understanding of the First Amendment. For example, when students were asked whether the First Amendment protects "hate speech," 4 in 10 said no. This is incorrect. Speech perceived as promoting hatred may be abhorrent, but it is constitutionally protected. Women are more likely than men to believe hate speech is not constitutionally protected (49 percent vs. 38 percent, respectively).

Students were asked whether the First Amendment requires that an offensive speaker at a public university be matched with one with an opposing view. Here, 6 in 10 (mistakenly) said that, yes, the First Amendment requires balance.

The most chilling findings, however, involved how students think repugnant speech should be dealt with. Villasenor offered a hypothetical that may sound familiar to those who recall recent fracases at California State University at Los Angeles, Middlebury College, Claremont McKenna College and other institutions:

Let's say a public university hosts a "very controversial speaker," one "known for making offensive and hurtful statements." Would it be acceptable for a student group to disrupt the speech "by loudly and repeatedly shouting so that the audience cannot hear the speaker"?

Astonishingly, half said that snuffing out upsetting speech -- rather than, presumably, rebutting or even ignoring it -- would be appropriate. Democrats were more likely than Republicans to find this response acceptable (62 percent to 39 percent), and men were more likely than women (57 percent to 47 percent). Even so, sizable shares of all groups agreed.

It gets worse.

Respondents were asked if it would be acceptable for a student group to use violence to prevent that same controversial speaker from talking. Here, 19 percent said yes.

There were no statistically significant differences in response by political party affiliation. Men, however, were three times as likely as women to endorse using physical force to silence controversial views (30 percent of men vs. 10 percent of women).

While colleges can do more to promote freer debate, they alone are not to blame for these findings. Other data suggest that freshmen are arriving on campus with more intolerant attitudes toward free speech than their predecessors did, and that Americans of all ages have become strikingly hostile toward basic civil and political liberties.

Colleges provide a crucible for America's increasingly strained attitudes toward free discourse. But they are just the canaries in the coal mine.

Catherine Rampell's column is distributed by the Washington Post Writers Group.