“What America is not understanding about what’s happening at Berkeley is this is a community and a campus that is under a comprehensive, well-funded full assault by the alt-right,” said Michael Mark Cohen, an associate professor of American studies and African-American studies who is helping lead the boycott. “These people will not leave us alone. This has to stop unless the rest of the country is willing to let Berkeley become a battlefield.”

Mr. Cohen says he would prefer for the university to bar inflammatory right-wing speakers from coming to campus and spend the money now going to security on legal fees defending the ban.

One view shared by people on both sides of the free speech debate is that the university’s role as a sanctuary of learning is being undermined by bands of outsiders who are using Berkeley’s reputation as a liberal bastion to prove a point. This month, Ben Shapiro, a right-wing writer, spoke at Berkeley amid a heavy police presence that cost the university $600,000. He said he wanted to prove that “there are students who do want to hear different views.”