In recent months, Mr. Falwell has been denounced for tweets involving Blackface and Ku Klux Klan imagery, as well as for his decision to reopen the campus in March as the coronavirus pandemic was exploding. (He has also sparred with news organizations covering the university, including The New York Times.)

But it was the photograph that ignited the largest uproar.

“There are limits,” Grant Wacker, professor emeritus of Christian history at Duke Divinity School, said. “Evangelicals will forgive an awful lot. But sexual transgression of that sort, pushing the line that hard,” he said, adding, “There are so many layers to it that are appalling.”

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“I don’t know if a secular institution would abide by a university president doing that — why should a Christian one?” Anthea Butler, a professor of religious studies at the University of Pennsylvania, said of Mr. Falwell’s behavior depicted in the post. “It’s pretty clear to them that he has become a liability to the school as opposed to an asset.”

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“Liberty University has always been what I call a culture war institution,” said John Fea, a professor of American history at Messiah College whose research focus includes evangelical Christianity. “It was born out of the culture war.”

Mr. Falwell has followed the political cues of his father, adapting the religious right his father helped create for a different era, and supporting Mr. Trump in a way the elder Mr. Falwell did with Ronald Reagan.

“The son really turned it up a notch,” Professor Fea said. “You saw just what Liberty was willing to do to defend these kind of values.”