In December 1964, a Silver Age of American liberalism, to rival the Golden Age of FDR and the New Deal, seemed to be upon us.

Barry Goldwater had been crushed in a 44-state landslide and the GOP reduced to half the size of the Democratic Party, with but 140 seats in the House and 32 in the Senate.

The Supreme Court of Chief Justice Earl Warren, the most liberal in history, was on a roll, and LBJ was virtually unopposed as he went about ramming his Great Society through Congress.

The left had it all. But then they blew it, beginning at Berkeley.

Protests, sit-ins, the holding of cops hostage in patrol cars—went on for weeks to force the University of California, Berkeley, to grant "free speech," and then "filthy speech" rights everywhere on campus.

Students postured as revolutionaries at the barricades, and the Academic Senate, consisting of all tenured faculty, voted 824-115 to support all Free Speech Movement demands, while cravenly declining to vote to condemn the tactics used.

Middle America saw the students differently—as overprivileged children engaged in a tantrum at the most prestigious school in the finest university system in the freest nation on earth.

Here is how their leader Mario Savio described the prison-like conditions his fellow students had to endure on the Berkeley campus in 1964:

"There is a time when the operation of the machine becomes so odious, makes you so sick at heart, that you can't take part; you can't even passively take part, and you've got to put your bodies upon the gears and upon the wheels, upon the levers, upon all the apparatus, and you've got to make it stop. And you've got to indicate to the people who run it, to the people who own it, that unless you're free, the machine will be prevented from working at all!"

To borrow from Oscar Wilde, it takes a heart of stone to read Mario's wailing—without laughing.

As I wondered in an editorial in the St. Louis Globe-Democrat that week, "If there is so much restriction of speech on the campus, how it is that a few yards from Sproul Hall there is a Young Socialist League poster complaining of 'American Aggression in the Congo' and calling on students to support 'the Congolese rebels.'"

Yet Berkeley proved a godsend to a dispirited right.

In 1966, Ronald Reagan would beat Berkeley like a drum in his run for governor, calling the campus, "a haven for communist sympathizers, protesters and sex deviants."

Reagan relished entertaining his populist following by mocking San Francisco Democrats. "A hippie," said the Gipper, "looks like Tarzan, walks like Jane and smells like Cheetah."

More seriously, the radicalism, intolerance, arrogance and fanaticism of the far left in the '60s and '70s helped to revive the Republican Party and bring it victories in five of the next six presidential elections.

In 1964, neither Nixon nor Reagan appeared to have a bright future. But after Berkeley, both captured the presidency twice. And both benefited mightily from denouncing rioting students, even as liberalism suffered from its perceived association with them.

Which brings us to Berkeley today.

Last week, columnist and best-selling author Ann Coulter was forced to cancel her speech at Berkeley. Her security could not be guaranteed by the university.

In February, a speech of Breitbart editor Milo Yiannopoulos also was canceled out of safety concerns after campus protesters hurled smoke bombs, broke windows and started a bonfire. The decision was made two hours before the event, as a crowd of 1,500 had gathered outside the venue.

The recent attacks on Charles Murray at Middlebury College and Heather Mac Donald at Claremont McKenna call to mind an event from three decades before Berkeley '64.

On Dec. 5, 1930, German moviegoers flocked to Berlin's Mozart Hall to see the Hollywood film, "All Quiet on the Western Front." Some 150 Brownshirts, led by Joseph Goebbels, entered the theater, tossed stink bombs from the balcony, threw sneezing powder in the air and released mice. Theaters pulled that classic anti-war movie.

That same sense of moral certitude that cannot abide dissent to its dogmatic truths is on display in America today, as it was in Germany in the early 1930s. We are on a familiar slippery slope.

First come the marches and demonstrations. Then the assertion of the right to civil disobedience, to break the law for a higher cause by blocking streets and highways. Then comes the confronting of cops, the smashing of windows, the fistfights, the throwing of stones - as in Portland on May Day.

And, now, the shouting down of campus speakers.

The rage and resentment of the left at its rejection in 2016 are palpable. Sometimes this fever passes peacefully, as in the "Cooling of America" in the 1970s. And sometimes it doesn't.

But to have crowds of left and right coming out to confront one another violently, in a country whose citizens possess 300 million guns, is probably not a good idea.

Patrick J. Buchanan needs no introduction to VDARE.COM readers; his books State of Emergency: The Third World Invasion and Conquest of America, and Suicide of a Superpower: Will America Survive to 2025? are available from Amazon.com. Patrick J. Buchanan is the author of “The Greatest Comeback: How Richard Nixon Rose From Defeat to Create the New Majority.

His latest book, out May 9, is "Nixon's White House Wars: The Battles That Made and Broke a President and Divided America Forever."