Republican presidential candidate Donald Trump makes a speech nearly every day. But in graduation season, a number of commencement speakers have used their time at the podium to challenge him and his rhetoric. Here are the highlights from Ken Burns, Matt Damon, Lin-Manuel Miranda and more. (Gillian Brockell/The Washington Post)

“For nearly forty years now, I have diligently practiced and rigorously maintained a conscious neutrality in my work, avoiding the advocacy of many of my colleagues, trying to speak to all of my fellow citizens,” the documentarian Ken Burns told the students, parents and faculty assembled at Stanford University’s commencement Sunday.

Shortly after stating the principles that have made him a wildly popular and influential interpreter of some of the most difficult moments in U.S. history, it became clear that Burns was reiterating this idea because he was about to depart from it. The speech that followed contained plenty of good life advice and affirmations of the communitarian ideals that have informed Burns’s work. And in addition to hitting the requisite marks, Burns launched a sharp and sweeping attack on Donald Trump’s campaign for the presidency that placed the GOP front-runner in a tradition that includes some of the ugliest impulses in U.S. political history.

I spoke to Burns last week, when he was still finalizing the Stanford address. He suggested at the time that the speech would break ground for him even in a year when he has already given the National Endowment for the Humanities’ Jefferson Lecture and embarked on a nationwide speaking tour that saw him grappling with the role of race in U.S. history. But if audiences who know Burns only through his most famous documentaries were surprised by the Stanford speech, they shouldn’t have been.

Burns has never shied away from making political — if not explicitly partisan — points in his documentaries. “The Civil War” pays particular attention to the role that both enslaved and free African Americans played in fighting for emancipation, and takes sharp aim at the violence of Nathan Bedford Forrest’s career as a Confederate general and as the post-war founder of the Ku Klux Klan. “The Dust Bowl” is a parable about both environmental stewardship and the harmful power of narrowly defined roles for women. “Jackie Robinson” debunks the myths that have grown up around the integration of baseball and emphasizes Robinson’s role as an advocate off the field after his playing career was over.

And Burns has been blunt in arguing that race is one of the great fault lines running through U.S. history and society.

Burns pushed hard for New York to reach a financial settlement with the Central Park Five, a group of young black and Latino men who were falsely convicted of raping and nearly killing a woman in an infamous, racially charged case that came to define a violent, polarized era in the city. Trump used the case and the Central Park Five’s trial as an opportunity to showboat and demagogue, foreshadowing his approach in the 2016 election. (Burns, his daughter Sarah, and Sarah’s husband, David McMahon, co-directed a 2012 film about the case.)

Last December, after the 2015 shooting at Emanuel African Methodist Episcopal Church in Charleston, S.C., Burns and Harvard’s Henry Louis Gates Jr. kicked off a national speaking tour in the city, using the first stop to raise money for a planned International African American Museum that will commemorate Charleston’s role in the slave trade.

That tour coincided with Trump’s rise as a Republican candidate, from joke to front-runner. When Burns and Gates came to Washington in March, they both warned against what Gates described as Trump’s dedication to “exploiting the contradictions in American society.”

Then, Burns placed Trump in the context of generations of politicians who encourage white voters to ignore their economic self-interest by appealing to crude identity politics. At Stanford on Sunday, Burns widened that lens, and sharpened it, focusing on the details that have propelled Trump’s rise.

“As a student of history, I recognize this type. He emerges everywhere and in all eras,” Burns said of Trump. “We see nurtured in his campaign an incipient Proto-fascism, a nativist anti-immigrant Know Nothing-ism, a disrespect for the judiciary, the prospect of women losing authority over their own bodies, African Americans again asked to go to the back of the line, voter suppression gleefully promoted, jingoistic saber rattling, a total lack of historical awareness, a political paranoia that, predictably, points fingers, always making the other wrong.”

But, Burns warned, what makes Trump especially dangerous is the convergence of these tendencies in a single candidate.

“These are all virulent strains that have at times infected us in the past,” he told the graduates, their parents and the Stanford faculty. “But they now loom in front of us again — all happening at once. We know from our history books that these are the diseases of ancient and now fallen empires. The sense of commonwealth, of shared sacrifice, of trust, so much a part of American life, is eroding fast, spurred along and amplified by an amoral Internet that permits a lie to circle the globe three times before the truth can get started.”

Even in Burns’s sharp attack on Trump’s qualifications and character, and on the media he suggested had abetted Trump’s rise in the age of ratings, there were notes of his inclination toward bipartianship.

“This is not a liberal or conservative issue, a red-state, blue-state divide. This is an American issue. Many honorable people, including the last two Republican presidents, members of the party of Abraham Lincoln, have declined to support him,” Burns said. “And I implore those ‘Vichy Republicans’ who have endorsed him to please, please reconsider. We must remain committed to the kindness and community that are the hallmarks of civilization and reject the troubling, unfiltered Tourettes of his tribalism.”

And in his advice to the graduates, Burns suggested that they “try not to make the other wrong, as I just did” in the sections of his address that mentioned Trump.

(Burns also acknowledged the controversy surrounding the sentence former Stanford student Brock Allen Turner received after he convicted of sexual assault, telling the audience, “I am the father of four daughters. If someone tells you they’ve been sexually assaulted, take it effing seriously. And listen to them! Maybe, someday, we will make the survivor’s eloquent statement as important as Dr. King’s Letter from a Birmingham Jail.”)

This is an election season where the rules governing public discourse haven’t merely been mildly eroded; they’ve been swept away entirely, as if by a ravaging flood. Trump may not have had a soul or social standing to lose in the campaigning process. But, as Burns suggested, the rest of the country does. And at extraordinary moments, we shouldn’t let our principles gag us from saying what is necessary.