“I would not deny,” Mr. Rothberg added, “that Professor Salaita’s tweets are frequently expressed in strong language, and I share what I imagine is your preference for a civil tone in public discourse. But there are moments — like the recent bombing campaign — when we may need to expand our notion of what constitutes an acceptable tone so that it is commensurate with the events at stake.”

Several of the comments that supporters of Israel took exception to referred to parallels Mr. Salaita has drawn in his work between the experiences of Native Americans and Palestinians. When he was recommended for tenure last year, this was seen by the university as a strength. “The uniqueness of his scholarship on the intersection of American-Indian, Palestinian, and American-Palestinian experiences,” one reviewer argued, “presents a rare opportunity to add an esoteric perspective on indigeneity to our cultural studies programs on campus.”

But last month, just two weeks before he was scheduled to begin work, the university’s chancellor abruptly informed Mr. Salaita that the job offer had been rescinded because approval by the trustees, who usually defer to faculty on hiring matters, was unlikely in his case. Her decision was strongly opposed by the American Indian Studies department and other members of the faculty who argued that it was an infringement of academic freedom.

In a blog post written last month, the chancellor insisted that her decision to stop Mr. Salaita from taking up his post “was not influenced in any way by his positions on the conflict in the Middle East nor his criticism of Israel.” The issue, she said, was the “uncivil” tenor of his comments, and concerns expressed by pro-Israel students who said that they would feel intimidated by the professor.

“What we cannot and will not tolerate at the University of Illinois,” Ms. Wise wrote last month, “are personal and disrespectful words or actions that demean and abuse either viewpoints themselves or those who express them.”

“It’s about feeling safe on campus,” Noah Feingold, a member of a pro-Israel student group, told The Forward. “This is a professor who tweeted that if you support Israel, you’re an awful person.”

A trove of internal university documents released after Freedom of Information requests showed that the chancellor acted after hearing from dozens of students and alumni, including donors to the university who threatened to stop giving if Mr. Salaita was allowed to teach at the school.