Ms. Wedatalla declined an interview request, and did not explain why she had not raised concerns before the image was shown. But in an email statement, she said images of Prophet Muhammad should never be displayed, and that Dr. López Prater gave a trigger warning precisely because she knew such images were offensive to many Muslims. The lecture was so disturbing, she said, that she could no longer see herself in that course.

Four days after the class, Dr. López Prater was summoned to a video meeting with the dean of the college of liberal arts, Marcela Kostihova.

Dr. Kostihova compared showing the image to using a racial epithet for Black people, according to Dr. López Prater.

“It was very clear to me that she had not talked to any art historians,” Dr. López Prater said.

A couple of weeks later, the university rescinded its offer to teach next semester.

Dr. López Prater said she was ready to move on. She had teaching jobs at other schools. But on Nov. 7, David Everett, the vice president for inclusive excellence, sent an email to all university employees, saying that certain actions taken in an online class were “undeniably inconsiderate, disrespectful and Islamophobic.”

The administration, after meeting with the school’s Muslim Student Association, would host an open forum “on the subject of Islamophobia,” he wrote.

Dr. López Prater, who had only begun teaching at Hamline in the fall, said she felt like a bucket of ice water had been dumped over her head, but the shock soon gave way to “blistering anger at being characterized in those terms by somebody who I have never even met or spoken with.” She reached out to Dr. Gruber, who ended up writing the essay and starting the petition.