In 1948, President Edmund Ezra Day of Cornell explained why his institution would never hire a Communist on its faculty. “It is a part of the established technique of Communistic activity to resort to deceit and treachery,” Day wrote. “A man who belongs to the Communist Party and who follows the party line, is thereby disqualified from participating in a free, honest inquiry after truth, and from belonging on a university faculty devoted to the search for truth.”

Plug in “Trump supporter” for “Communist,” and you get a pretty good sense of what’s happening on our campuses right now. Students and faculty are demanding that universities sever ties with anyone who worked in the Trump administration or backed President Trump’s efforts to overturn the 2020 election. And the rationale is the same one that was used against Communists and so-called fellow travelers during the Cold War: They don’t believe in democracy, so they don’t belong at a university devoted to it.

But that perverts the democratic ideal, all in the guise of preserving it. The real threat isn’t a horde of evil Trumpers clamoring at our gates. It’s our quest to root out the enemies of democracy, which never ends well for the university.

Witness a student petition that circulated at Harvard in November, shortly after Joe Biden defeated Donald Trump, urging the university to establish a new “system of accountability” to review whether former Trump officials could come to campus as professors, fellows, or speakers. Anyone who had engaged in “the subversion of democratic principles” should not be invited, the petition urged.

“A complete disregard for the truth is a defining feature of many decisions made by this administration,” the petition charged, referencing the Trump White House. “That alone should be enough to draw the line.”

But how can we decide who is honest enough to teach or speak at Harvard? After the January 6 assault on the Capitol, the government professor Ryan Enos put forward his own standard: Anyone who “aided a violent insurrection” should be barred from the institution. In a letter to President Lawrence Bacow of Harvard, Enos emphasized that he was “a firm believer in academic freedom.” But members of Congress who sought to overturn the election and “emeritus faculty” who defended Trump should not be allowed to work or speak at the university.

That was a none-too-subtle swipe at U.S. Rep. Elise Stefanik, Republican of New York, an advisory-board member of the Institute of Politics at Harvard’s John F. Kennedy School of Government, who had repeated Trump’s unsubstantiated charges of fraud and refused to certify electoral votes from Pennsylvania on the evening of the riot. Nor was it hard to identify the emeritus professor in Enos’s letter: Alan Dershowitz, one of Trump’s lawyers in his first impeachment trial.

In short order, Dean Doug Elmendorf of the Kennedy School removed Stefanik from the Institute of Politics’ 13-member advisory board — not because of her “political ideology,” he said, but because of her false claims about the election. “These assertions and statements do not reflect policy disagreements but bear on the foundations of the electoral process,” Elmendorf wrote.

That seems like a simple dividing line, at first glance: Supporters of Trump are OK, so long as they didn’t support the overthrow of the election. But in practice, these categories can easily meld into each other.