Something ugly has been happening on some college campuses. Several have reported anti-Semitic incidents and some Jewish students are complaining of a hostile, almost threatening, atmosphere. Much of the unrest can be traced to clashing ideas about the Israeli-Palestinian conflict. That’s what a campus is for: a clash of ideas. But the rhetoric has sometimes translated into hate and violence.

At the University of Colorado’s Boulder campus a holiday booth set up by Jewish students was defaced with swastikas, and anti-Semitic graffiti was scribbled on a Jewish fraternity house.

Students at San Francisco State University yelled “Death to Jews!” and “Hitler should have finished the job!” at a pro-Israel demonstration last May.

At the University of California at Berkeley, someone tossed a cinder block through the glass door of the campus Hillel center for Jewish students and spray-painted anti-Semitic slogans on the wall last spring.

At Montreal’s Concordia University, pro-Palestinian demonstrators broke windows and stormed a lecture hall where former Israeli Prime Minister Benjamin Netanyahu was to speak in September.

Those incidents and others prompted more than 300 university and college presidents to sign a newspaper ad decrying “threats, taunts or intimidation” against Jewish students and vowing to “sustain an intimidation-free campus.”

Following student complaints, the University of Chicago brought in counselors from the Anti-Defamation League this fall to give dormitory advisers training to help students work out differences in a respectful manner.

There is a natural ebb and flow of debate on campus. Ideas come into fashion and then fade. But what underpins everything is the freedom to question, to think critically about issues and express an opinion without fear. If that is being squelched, then universities should take action.

Across Europe, where anti-Semitic incidents are on the rise, a similar sentiment has prompted the blacklisting or firing of Israeli academics.

Israel can be criticized for much in its treatment of the Palestinian people. That is and should be part of a broad human rights debate that includes the repressive regime of Saudi Arabia, the Syrian occupation of Lebanon, even the corrupt and stifling government in Egypt.

Beyond the Middle East are repressive dictatorships with “human rights records that might make Saddam Hussein flinch,” as Northwestern University law professor Steven Lubet recently wrote. North Korea lets uncounted multitudes of its citizens starve. In Nigeria, a woman was sentenced to be stoned to death for adultery.

Those human rights abuses, however, provoke virtually no protest on campus.

Colleges are supposed to be institutions of enlightenment and critical thinking, teaching tolerance and an appreciation for diversity. Instead, some college presidents now fear, the prevailing campus atmosphere is fostering a new generation of anti-Semites. Students need to be taught to think critically–as in skeptically, demandingly, but also fairly. The truth emerges through healthy debate and disagreement–not with hate and violence.