For several years now, scholars have argued that the world is experiencing a "democratic recession." They have noted that the movement of countries toward democracy has slowed or stopped and even, in some places, reversed.
They also note a general hollowing out of democracy in the advanced, industrial world. When we think about this problem, inevitably and rightly we worry about Donald Trump, his attacks on judges, the free press and his own Justice Department.
But there is also a worrying erosion of a core democratic norm taking place on the left.
It has become commonplace to hear cries on the left to deny controversial figures on the right a platform to express their views. Colleges have disinvited speakers like Condoleezza Rice and Charles Murray. Other campuses were unwilling or unable to allow conservative guests to actually speak, with protests overwhelming the events.
A similar controversy now involves Steve Bannon, who, in recent months, has been making the rounds on the airwaves and in print — including an interview I did with him on CNN. Some have claimed that Bannon, since leaving the administration, is simply unimportant and irrelevant and thus shouldn't be given a microphone.
But if that were the case, surely the media, which after all is a for-profit industry, would notice the lack of public interest and stop inviting him.
The reality is that the people running The Economist, The Financial Times, CBS's "60 Minutes," The New Yorker and many others who have recently sought to feature Bannon know that he is an intelligent and influential ideologist, a man who built the largest media platform for the new right, ran Trump's successful campaign before serving in the White House, and continues to articulate and energize the populism that's been on the rise throughout the Western world.
He might be getting his 15 minutes of fame that will peter out, but, for now, he remains a compelling figure.
The real fear that many on the left have is not that Bannon is dull and uninteresting, but the opposite — that his ideas will prove seductive and persuasive to too many people.
Hence his detractors' solution: Don't give him a platform, and hope that this will make his ideas go away. But they won't. In fact, by trying to suppress Bannon and others on the right, liberals are likely making their ideas seem more potent. Did the efforts of communist countries to muzzle capitalist ideas work?
Liberals need to be reminded of the origins of their ideology. In 1859, when governments around the world were still deeply repressive — banning books, censoring commentary and throwing people in jail for their beliefs — John Stuart Mill explained in his seminal work, "On Liberty," that protection against governments was not enough: "There needs protection also against the tyranny of the prevailing opinion and feeling; against the tendency of society to impose . . . its own ideas and practices . . . on those who dissent from them."
This classic defense of free speech, which Supreme Court Justice Oliver Wendell Holmes later called the "freedom for the thought that we hate," is under pressure in America — and from the left.
We've been here before. Half a century ago, students were also shutting down speakers whose views they found deeply offensive.
In 1974, William Shockley, the Nobel Prize-winning scientist who in many ways was the father of the computer revolution, was invited by Yale students to defend his abhorrent view that blacks were a genetically inferior race who should be voluntarily sterilized.
He was to debate Roy Innis, the African-American leader of the Congress of Racial Equality. (The debate was Innis' idea.)
A campus uproar ensued and the event was cancelled.
A later, rescheduled debate with another opponent was disrupted.
The difference from today is that Yale recognized that it had failed in not ensuring that Shockley could speak. It commissioned a report on free speech that remains a landmark declaration of the duty of universities to encourage debate and dissent.
The report flatly states that a college "cannot make its primary and dominant value the fostering of friendship, solidarity, harmony, civility or mutual respect. . . . It will never let these values . . . override its central purpose. We value freedom of expression precisely because it provides a forum for the new, the provocative, the disturbing and the unorthodox."
The report added: "We take a chance, as the First Amendment takes a chance, when we commit ourselves to the idea that the results of free expression are to the general benefit in the long run, however unpleasant they may appear at the time."
It is on this bet for the long run, a bet on freedom — of thought, belief, expression and action — that liberal democracy rests.
Fareed Zakaria hosts CNN's "Fareed Zakaria GPS," and makes regular appearances on shows such as ABC's "This Week" and NBC's "Meet The Press." He has been an editor at large Time magazine since 2010, and spent 10 years overseeing Newsweek's foreign editions. He is a Washington Post (and internationally syndicated) columnist. He is author of "The Post-American World." For more of Fareed Zakaria's reports, Go Here Now.