Democratic leader in the U.S. Senate, Chuck Schumer, acted like an ass in a Manhattan restaurant recently when he learned a Democratic friend and colleague’s wife, the daughter of the founder of CBS, voted for Donald Trump.

He was dining with friends when he encountered Joseph A. Califano Jr. — the former U.S. secretary of health, education and welfare under President Jimmy Carter and domestic policy adviser to President Lyndon B. Johnson — and his wife, Hilary, who were having a quiet dinner.

Onlookers said Schumer was incensed that Hilary — the daughter of William S. Paley, the founder and chairman of CBS — had voted for Trump, even though her husband, Joseph, is a well-known Democrat.

One witness said of the restaurant rant, “They are a highly respected couple, and Schumer made a scene, yelling, ‘She voted for Trump!’ The Califanos left the restaurant, but Schumer followed them outside.” On the sidewalk, Schumer carried on with his fantastical filibuster: “ ‘How could you vote for Trump? He’s a liar!’ He kept repeating, ‘He’s a liar!’ ”

Hilary confirmed the confrontation, telling Page Six, “Sen. Schumer was really rude . . . He’s our senator, and I don’t really like him. Yes, I voted for Trump. Schumer joined us outside and he told me Trump was a liar. I should have told him that Hillary Clinton was a liar, but I was so surprised I didn’t say anything.”

Notice how Schumer handles dissenting opinion: with rage, intimidation and intolerance. You’d expect a man who preens in front of the public for a living, and who runs one of America’s two major political parties in the most public job imaginable, would have a little more self-control. But he doesn’t. Why not? Because he does not feel obliged to do so. Like many of his fellow progressives, he feels entitled to impose his views in any way he wishes, even when his views are neither solicited nor appreciated.

What fuels such rage and intolerance? It’s beyond being a sore loser. The election was months ago. Democrats like Schumer already are licking their chops over a return to power, and not without reason given the Republican compulsion for snatching defeat from the jaws of victory again, and again and yet again. (Latest example: Refusing to propose an outright repeal of Obamacare in Congress, as promised for the last 7 years).

The rage and intolerance stems from the ideology of leftism itself. Think about what leftism is: force and compulsion. I won’t deny that the right is guilty of the same. But the right is more mixed. It’s a combination of liberty and compelling people to do things the government has no business making them do. Leftism, on the other hand, is almost exclusively about a big, intrusive federal government telling you what to do. It’s undiluted authoritarianism.