Two dozen students walked out of their classroom at Drexel University in Philadelphia last month carrying signs that read “Where is our professor?” and “Bring back GCM.” They felt they had a pressing reason to protest. “For 40-plus days, we’ve been without a professor in the classroom,” said Dakota Peterson, a 22-year-old political science student.

Their professor, George Ciccariello-Maher, has been teaching his class remotely via video conference after the university put him on administrative leave. He’s not allowed on campus without a police escort. The school says his enforced absence is due to safety concerns raised by a furious and frightening reaction to controversial posts he made on social media.

Ciccariello-Maher, who teaches politics and global studies, said he’s received numerous death threats over the last 12 months. “I have 800 unread voicemails in my inbox right now that have been building up over the past few weeks. And this …

it’s just something that happens all the time,” he said. “Threats that involve my child are, of course, the ones that are the most frightening to me.”Professors who thought that their classrooms and social media forums are safe places to discuss controversial ideas are learning they have a much wider and more vindictive audience than they imagined.”There’s an entire cottage industry for reporting on controversial things that faculty members say, which then riles up internet outrage mobs, who then start to tweet at schools, or post on Facebook, and try to get schools to get rid of people who they disagree with,” Cohn says.

One of the websites, called Professor Watchlist, was started by Charlie Kirk.”Our goal is to expose and really profile professors that have engaged in outward radical behavior,” said Kirk. “We’re not saying these professors should be silenced. Instead, we’re pointing out what has become a systemic problem in our universities, where professors are able to say things that are completely outrageous.”