Professors have long been political targets. But a spate of recent threats against scholars — including two that have led to campus closures — is raising fresh concerns about safety and academic freedom.

The American Associations of University Professors “is definitely concerned about this trend, which I think is a fair description of what is happening,” said Hans-Joerg Tiede, senior program officer for academic freedom and tenure at AAUP. “We will continue to monitor it and consider what other actions we can take.”

First, a roundup of cases:

• In early May, Tommy J. Curry, associate professor of philosophy at Texas A&M University, faced death threats and race-based harassment for talking about violence against whites in a 2012 podcast interview about the gory Quentin Tarantino film Django Unchained. Portions of Curry’s opinions were quoted in right-wing publications, where he was portrayed as advocating violence.
• Bret Weinstein, a professor of biology at Evergreen State College, was in May warned to stay off that campus by security officials after he questioned the logic of a student request that all white students and faculty members stay away during a day of protest. The college temporarily shut down after further threats and demands from some students that Weinstein be fired.
• Keeanga-Yamahtta Taylor, an assistant professor of African-American studies at Princeton University, canceled planned public talks this month, saying she received hateful messages and death threats for criticizing President Trump in a commencement speech at Hampshire College.
• Sarah Bond, an assistant professor of classics at the University of Iowa, faced threats and harassment — some of it anti-Semitic — after publishing a piece in Hyperallergic. She argued that classicists should do more to highlight the fact that statues were often painted and so not necessarily reflective of the “classical ideal” now equated with white marble. Bond’s views are widely backed by scholars in her field.
• At Syracuse University, Dana Cloud, a professor of communication and rhetoric, was the subject of threats and harassment after she tweeted for counterdemonstrators to join her and “finish off” a dispersing group of protesters against Islamic law.
• Most recently, Johnny Eric Williams, an associate professor of sociology at Trinity College in Connecticut, said he had to flee town due to threats — and the campus shut down for a day — after conservative news websites shared Facebook posts he made about race. He used the hashtag #LetThemFuckingDie in response to an online article about racism of the same name. Some have argued he was advocating violence against whites, but he’s since said he was referring to systemic racism.