The recent flurry of marches, demonstrations and even riots, along with the Democratic Party’s spiteful reaction to the Trump presidency, exposes what modern liberalism has become: a politics shrouded in pathos. Unlike the civil-rights movement of the 1950s and ’60s, when protesters wore their Sunday best and carried themselves with heroic dignity, today’s liberal marches are marked by incoherence and downright lunacy—hats designed to evoke sexual organs, poems that scream in anger yet have no point to make, and an hysterical anti-Americanism.

All this suggests lostness, the end of something rather than the beginning. What is ending?

America, since the ’60s, has lived through what might be called an age of white guilt. We may still be in this age, but the Trump election suggests an exhaustion with the idea of white guilt, and with the drama of culpability, innocence and correctness in which it mires us.

White guilt is not actual guilt. Surely most whites are not assailed in the night by feelings of responsibility for America’s historical mistreatment of minorities. Moreover, all the actual guilt in the world would never be enough to support the hegemonic power that the mere pretense of guilt has exercised in American life for the last half-century.

White guilt is not angst over injustices suffered by others; it is the terror of being stigmatized with America’s old bigotries—racism, sexism, homophobia and xenophobia. To be stigmatized as a fellow traveler with any of these bigotries is to be utterly stripped of moral authority and made into a pariah. The terror of this, of having “no name in the street” as the Bible puts it, pressures whites to act guiltily even when they feel no actual guilt. White guilt is a mock guilt, a pretense of real guilt, a shallow etiquette of empathy, pity and regret.

It is also the heart and soul of contemporary liberalism. This liberalism is the politics given to us by white guilt, and it shares white guilt’s central corruption. It is not real liberalism, in the classic sense. It is a mock liberalism. Freedom is not its raison d’être; moral authority is.

When America became stigmatized in the ’60s as racist, sexist and militaristic, it wanted moral authority above all else. Subsequently the American left reconstituted itself as the keeper of America’s moral legitimacy. (Conservatism, focused on freedom and wealth, had little moral clout.) From that followed today’s markers of white guilt—political correctness, identity politics, environmental orthodoxy, the diversity cult and so on.

This was the circumstance in which innocence of America’s bigotries and dissociation from the American past became a currency of hardcore political power. Barack Obama and Hillary Clinton, good liberals both, pursued power by offering their candidacies as opportunities for Americans to document their innocence of the nation’s past. “I had to vote for Obama,” a rock-ribbed Republican said to me. “I couldn’t tell my grandson that I didn’t vote for the first black president.”

For this man liberalism was a moral vaccine that immunized him against stigmatization. For Mr. Obama it was raw political power in the real world, enough to lift him—unknown and untested—into the presidency. But for Mrs. Clinton, liberalism was not enough. The white guilt that lifted Mr. Obama did not carry her into office—even though her opponent was soundly stigmatized as an iconic racist and sexist.

Perhaps the Obama presidency was the culmination of the age of white guilt, so that this guiltiness has entered its denouement. There are so many public moments now in which liberalism’s old weapon of stigmatization shoots blanks—Elizabeth Warren in the Senate reading a 30-year-old letter by Coretta Scott King, hoping to stop Jeff Sessions’s appointment as attorney general. There it was with deadly predictability: a white liberal stealing moral authority from a black heroine in order to stigmatize a white male as racist. When Ms. Warren was finally told to sit, there was real mortification behind her glaring eyes.

This liberalism evolved within a society shamed by its past. But that shame has weakened now. Our new conservative president rolls his eyes when he is called a racist, and we all—liberal and conservative alike—know that he isn’t one. The jig is up. Bigotry exists, but it is far down on the list of problems that minorities now face. I grew up black in segregated America, where it was hard to find an open door. It’s harder now for young blacks to find a closed one.

This is the reality that made Ms. Warren’s attack on Mr. Sessions so tiresome. And it is what caused so many Democrats at President Trump’s address to Congress to look a little mortified, defiantly proud but dark with doubt. The sight of them was a profound moment in American political history.

Today’s liberalism is an anachronism. It has no understanding, really, of what poverty is and how it has to be overcome. It has no grip whatever on what American exceptionalism is and what it means at home and especially abroad. Instead it remains defined by an America of 1965—an America newly opening itself to its sins, an America of genuine goodwill, yet lacking in self-knowledge.

This liberalism came into being not as an ideology but as an identity. It offered Americans moral esteem against the specter of American shame. This made for a liberalism devoted to the idea of American shamefulness. Without an ugly America to loathe, there is no automatic esteem to receive. Thus liberalism’s unrelenting current of anti-Americanism.

Let’s stipulate that, given our history, this liberalism is understandable. But American liberalism never acknowledged that it was about white esteem rather than minority accomplishment. Four thousand shootings in Chicago last year, and the mayor announces that his will be a sanctuary city. This is moral esteem over reality; the self-congratulation of idealism. Liberalism is exhausted because it has become a corruption.

Mr. Steele, a senior fellow at Stanford University’s Hoover Institution, is author of “Shame: How America’s Past Sins Have Polarized Our Country” (Basic Books, 2015).