On Tuesday, Arizona Sen. Jeff Flake became the latest Republican to denounce President Trump. Flake blasted Trump's "reckless, outrageous, and undignified" behavior, echoing recent statements by Tennessee Sen. Bob Corker and former President George W. Bush. Under Trump, Flake argued, American politics has become a nonstop slugfest of  invective and falsehood.

"We must never regard as normal the regular and casual undermining of our democratic norms and ideals," Flake warned, announcing that he would not seek reelection. "The personal attacks, the threats against principles, freedoms and institutions, the flagrant disregard for truth and decency."

I thought of Flake's remarks as I read about the latest dust-up at my own institution, the University of Pennsylvania, over a teaching assistant who said she calls on minority and female students first. You'd like to think that a university — of all places — could discuss such a matter in a dignified and mutually respectful manner.

Think again. What we've learned, over the last few days, is that our educational institutions are every bit as intemperate and hostile as the rest of our political culture. Instead of teaching our students — and our country — a better way to talk, we have descended into Trump's nasty vortex of careless name-calling and vituperation.

The Penn controversy began when Stephanie McKellop, a Ph.D. student in history and a teaching assistant in a course on race and sex in early America, posted a tweet about the way she conducts her classes. "I will always call on my Black women students first," McKellop wrote. "Other POC get second tier priority. WW come next. And, if I have to, white men." (For the uninitiated, "POC" are people of color; "WW" are white women.)

The reaction in the blogosphere was fast, furious, and predictably polarized. On one side: angry right-wingers, denouncing McKellop as a man-hating racist and a politically correct social-justice warrior. On the other: her left-wing defenders, insisting that anyone who criticized her was a white supremacist.

To be fair, some of these comments came from people unconnected to the university. And a small handful of them analyzed McKellop's tweet in a fair-handed way, critiquing or supporting it with reason, logic, and evidence.

But the vast majority of posters felt no need to do that. They went straight for the jugular, engaging in precisely the kind of callous and uniformed attacks that Jeff Flake indicted.

I don't know Stephanie McKellop, and I have no idea how she conducts her class.  But here's the important point: neither do her critics, or her supporters. Except for a few of her students and ex-students, nobody who waded into this mess knew a thing about what McKellop actually does. And they didn't seem to want to know, either.

But when it comes to teaching, the devil is in the details. How often does McKellop call on minority and female students? If minorities and women are participating, but white men aren't, will she call on the white men? Is the sequence described in her tweet a hard-and-fast rule, or does she adjust it in accord with the tenor and spirit of her class?

When you believe you have a monopoly on truth, however, you don't have to trouble yourself with facts. So almost nobody in this dispute did. They simply assumed that McKellop was evil incarnate or a champion of good, depending on their politics, and they took it from there.

And that diverted us from the real question at hand: Is it fair to call on minorities or women first? McKellop's tweet reflected a practice called "progressive stacking," which has become popular in some pedagogic precincts over the last few years. The theory goes like this: Because racial minorities and women have less power and voice in our society, teachers need to take special steps to elicit — and, sometimes, to privilege — these voices in the classroom.

I can imagine many legitimate and reasonable objections to progressive stacking. By calling on members of certain groups first, aren't you denying their individuality? Some of them may indeed feel muzzled or silenced in the classroom, but others won't. If you assume they are victims of a racist or sexist culture, you might be patronizing them in the guise of protecting them.

Or: If your topic of discussion is race and sex, as in McKellop's course, you might actually stigmatize minorities and women if you solicit their views first. They might feel as if you have rendered them into spokespeople for their race or sex, an unenviable position for any of us.

But we won't be able to conduct a real conversation about progressive stacking — or about anything else — if we simply demean one another, without taking the time to learn anything new. Last I checked, that was the whole point of a university. Too bad that so many of us have lost sight of it, sinking into the same hostile muck where Donald Trump lives.

The biggest danger to our democracy is our arrogant and ignorant president. And the second-biggest danger is that the rest of us — on every side — are imitating him.

Jonathan Zimmerman teaches education and history at the University of Pennsylvania. He is the author (with Emily Robertson) of  "The Case for Contention: Teaching Controversial Issues in American Schools" (University of Chicago Press). jlzimm@aol.com