“You know,” the late William F. Buckley Jr. once mused, “I’ve spent my life separating the right from the kooks.” The conservative commentator was famously pugilistic, an ideological brawler, in fact, unrelentingly caustic, if eruditely so, about what he regarded as the deeply misguided policy prescriptions of liberal Democrats.

Buckley was devilish at locating the holes in liberals’ arguments, and he was accorded the status of devil by many of them. This was especially so in the 1960s and 1970s, when the combined divisions over Vietnam, civil rights and feminism produced an embittered polarization, which, at the time, seemed worse than anything we’d experienced since the Civil War.

In his new biography “Buckley: The Life and the Revolution That Changed America,” historian Sam Tanenhaus rightly assesses that Buckley was the intellectual architect of the modern conservative movement that carried Ronald Reagan to the White House in 1980. Buckley is less frequently recognized for the civility that he brought to his political combat than for all the zeal that he also brought to it. His weekly television show, “Firing Line,” featured thoughtful debates between him and Black liberationists, what at the time were thought of as militant feminists, and far-left ideologues. Derisive of critics of American policy in Vietnam, he counted as among his cherished friends two of America’s most prominent anti-war leaders: liberal economist John Kenneth Galbraith and Allard Lowenstein, who spearheaded the anti-war movement that forced Lyndon Johnson out of the 1968 presidential race. When Lowenstein was assassinated, Buckley flew halfway across the world to join Sen. Edward Kennedy in giving an emotional eulogy for their mutual friend.

Buckley would have been revolted by Donald Trump’s crude thuggery. He would have been appalled at the hatred that has broadly consumed America over the last decade, a hatred flowing from all directions, and which is eating America alive.

Last week’s massacre at Minneapolis’ Annunciation Church is simply the latest in a steady stream of murders by extremism-fueled American lunatics. The ravings of this lunatic have become all too familiar: “Six million wasn’t enough.” “Israel must fall.” “Kill Donald Trump.” “I hate those entitled, penny-sniffing kikes.” “I am a terrorist.” And so on, ad nauseam, with copious homages to other mass murderers.

The slaughter will be attributed to the prevalence of mental illness in America and the prevalence of guns here, and there’s truth to that. But there’s plenty of mental illness elsewhere, and the easy availability of guns in America isn’t a recent development.

What we’ve got here is a raging, out of control hatred problem. It spews from right and left. We’ve got a president who revels in his cruelty, who openly praises white supremacists and domestic terrorists, who incited a coup and then pardoned those who tried to execute it, who ridiculed 82-year-old Paul Pelosi after he had been savagely attacked by an assailant who intended to murder Trump’s political opponent. We’ve never seen anything like this.