The asymmetry of modern politics is clear to every conservative; painfully clear to several Yale undergraduates who asked me about it recently. Leftists, they pointed out, are hostile, nasty, and seem to have no concept of a civil conversation. Why? Because they are winning? Losing? Are natural-born bullies? And how can this dangerous mood be changed?

It’s not just a question of civility versus rudeness—which of course is no small thing in itself. The deeper problem is that the left seems to have lost its taste for democracy.

Naturally there are exceptions to the modern trend, benign leftists and nasty rightists. (Trump is a special case: see below.) The trend itself is partly explained by the Obama sneer; presidents have enormous influence. FDR's bouncy, feisty smile, Reagan's geniality, Clinton's one-of-the-boys grin, W's good-natured earnestness are part of history; and Obama's real "legacy" (aside from worldwide crisis) is that bitter sneer. His rudeness to political opponents has made a rotten political climate much worse. But the left's growing reputation for belligerent intolerance transcends Obama.

You see characteristic leftist arrogance among global warmers, who show their respect for their opponents by refusing to listen to them and implying that they are crackpots. On campus, leftists have spit at conservatives, screamed obscenities at moderate liberals, yammered on about phony "rape crises" while doing everything they could think of to promote universal debauchery, rigged local votes to silence opponents of the Kill Israel (aka "BDS") movement.

The list goes on, the arrogance is staggering, the asymmetry all too obvious. Conservatives, bursting with facts and ideas (and anger and dismay), are eager to have it out with liberals and maybe even convince a few. Liberals are eager to make assertions and strike moral poses, but not to respond to rational argument or speak to the facts.

Where does the asymmetry come from? American conservatives tend to be Christians or Jews. Liberals tend to be atheists or agnostics. (Yes, there are exceptions—to nearly everything, always; but that doesn't mean we can stop thinking.) Almost all human beings need religion, as subway-riders need overhead grab bars. The religious impulse strikes conservatives and liberals alike. But conservatives usually practice the religion of their parents and ancestors; liberals have mostly shed their Judaism or Christianity, and politics fills the obvious spiritual gap. You might make football, rock music, or hard science your chosen faith. Some people do. But politics, with its underlying principles and striking public ceremonies, is the obvious religion substitute.

Hence the gross asymmetry of modern politics. For most conservatives, politics is just politics. For most liberals, politics is their faith, in default of any other; it is the basis of their moral life.

Traditional religion used to be the iron grate that kept worldly beliefs from falling into the flames and turning into red-hot religious convictions in their own right. Among most conservatives it still is.

But for modern liberals it is only natural to be upset, defensive, dogmatic, and immovable when you are challenged on your political views. Few of us are prepared to defend our deepest spiritual beliefs. Most of us rarely think about them. Many of us have never had reason to believe them; we simply believe what our parents did. That is perfectly fair and suitable—except when rational, worldly politics is forced to confront politics-as-religion head-to-head.

Why should this new and dangerous virus have broken out now, in our generation? Judeo-Christian religion has been in decline for centuries. But important milestones have passed in our own lifetimes. Baby boomers were educated, in the '50s and '60s, in public schools that were still informally Christian—in a nation that (moreover) had been created by devout Christians guided by biblical ideas, and refounded during the Civil War by another Christian generation led by the most deeply religious of all our presidents. By the generation following the Second World War, it's likely that the U.S. cultural leadership was already mostly atheist. But it was reticent about saying so; in that era, many Americans still hesitated to go all the way. And the centrality of biblical religion to America's best self was reaffirmed during these same years by the pastors, priests, and rabbis of the civil rights movement. Today all these hugely important facts have been suppressed. My impression, as a college teacher, is that most young Americans have simply never heard them.

So here we are today with a mainstream press, cultural leadership, and intellectuals who laugh off the idea that a presidential candidate's religion matters. Yet it matters intensely. Its real, practical importance is large. Unless you are a Jew or Christian, you are likely—as a modern American—to make a religion of your politics. And that will shape, in turn, your relation to the opposition and to the American people.

Obama is probably our first atheist president. (David Bernstein noted in Mosaic that Obama's Hanukkah declaration this year did not manage to squeeze in a mention of God. One more small fact among many.) If Obama is indeed an atheist, I don't blame him for not saying so; in today's political environment, he can't. (Things will likely change fast in coming years.) Much of his crude contempt for his political opponents is the man himself. But that leaves plenty left over to reflect his outrage when you question his political beliefs—which happen to be (I believe) the foundation of his identity as a human being. All devout believers have moments of doubt—but that doesn't make them indifferent to wise-guy strangers casually kicking holes in their religion. Of course Obama is testy when you question his statist or appeasement-based policies. Those ideas are his religion, they are him, they are the spiritual fuel that keeps him going. Naturally any leftist who has got rid of his ancestral religion and replaced it with politics will be annoyed when you treat his political views like mere political views.

Some people are arrogant by nature. Obama, Hillary, and Trump are textbook examples. They were born that way. But Obama got help along the way from left-wing religion—whereas Hillary and Trump probably rank among the few human beings who love themselves so much, they don't need any kind of religion. Trump, of course, is no more a right-winger than Hillary is a true leftist: They each ad lib their fundamental beliefs as required.

My students want to know: How can this possibly go on? But how can it change? How can we rearrange this bloody-minded political atmosphere? My guess is that only a religious revival, or a Euro-style religious collapse, will change it. Obviously the collapse is far more likely than the revival. But revivals have happened before. America's soft spot is its children, and children—my guess is—are the only energy source strong enough to power a modern revival. A book on "Why Children Need God" and an associated movement, with left-wing pediatricians and psychiatrists arguing that children reared in traditional religious communities grow up happier and better put-together, might do the trick. But it will take a miracle.

David Gelernter, a professor of computer science at Yale, is a contributing editor to The Weekly Standard .