Hardly a week — and sometimes barely an hour — goes by without someone complaining loudly and earnestly about rampant violations of free speech marring American civic life.

The latest high-profile example is Tucker Carlson. Confronted by decade-old transcripts of Carlson calling into a right-wing radio show to express misogynistic views, the primetime Fox News host has defended himself as a martyr for free speech. As far as Carlson is concerned, Media Matters, the liberal muckraking outfit that unearthed and publicized the transcripts, is trying to silence him. But they cannot be allowed to succeed. Nothing less than freedom itself is at stake.

The Carlson kerfluffle will be forgotten any minute, but we can know for certain that it will be repeated in another guise before long. If cable news, talk radio, and social media are to be believed, these are dark days for free speech in America — on college campuses above all, but increasingly throughout our public life. We all need to be on guard about the threat.

Except that "free speech" as a constitutional principle is hardly ever involved in what gets described as threats to freedom of speech. It's crucially important that we recognize this fact, and come to understand what's really going on instead.

The First Amendment protects freedom of speech, and since the mid-20th century it has been interpreted by the Supreme Court to allow a nearly unlimited right of citizens to express themselves. Aside from very narrow categories of so-called fighting words, along with facts and ideas that are proscribed for pressing national security reasons, the federal government permits Americans to say pretty much anything they want without fear of prosecution. There is therefore no free speech crisis in the United States today. We live in a remarkably open society, with the government doing very little to police the boundaries of permissible speech.

Yet we are repeatedly told otherwise. How can that be? Because those raising concerns about restrictions on speech don't mean "free speech" in the strict, constitutional sense. They use the same term to mean something else — something that might be more accurately called a "culture of free speech," which they consider to be under assault in an informal (non-legal) sense. By this they mean that people in positions of cultural authority are attempting to delineate what can and cannot be said in public by threatening transgressors with moral denunciation, ridicule, humiliation, and other informal social and potentially economic penalties. (The latter kick in when the transgressor loses business, sponsors, or is fired for what he or she has said.)

Let's call this the "Millian move," after John Stuart Mill, the influential 19th-century liberal theorist who defended an open marketplace of ideas as the best way for people to freely make their way to the truth. I have a lot of sympathy for this ideal — on university campuses no less than in civil society at large.

But here's the thing: No society in human history has ever had a completely open marketplace of ideas, and no society ever will. Societies always informally proscribe some ideas as morally beyond the pale. That's one of the ways they encourage and cultivate social cohesion — keeping the political community in one piece and preventing it from splintering and flying apart in different directions.

Imagine if a public figure were to tweet out that he thinks Hitler's final solution was a good idea and should be taken up again by the president of the United States as soon as possible. That statement would be legally permissible in the United States (though it probably wouldn't be in Germany or France). But the person who uttered it would be instantly cast out — fired, evicted, and rendered socially radioactive by nearly everyone. And most of us would consider that a perfectly appropriate response — even, I suspect, the supposed free speech absolutists who make up the self-described Intellectual Dark Web. The same fate would almost certainly befall anyone who declared himself firmly convinced that pre-pubescent children should be forcibly inducted into sex acts.

The truth is that there is no such thing as a culture of absolutely free speech. This is true of all societies, even liberal ones. The question is always where cultural authorities draw the line between morally acceptable and unacceptable utterances. Once we recognize this reality, the distinctive problems of the present come into focus: Our arguments about "free speech" are really disputes about where to draw that line — and who gets to draw it. We increasingly lack consensus about what moral standards should be informally affirmed and upheld. We also lack consensus about which cultural authorities, if any, should enforce those standards.

Yet, strangely, we also love arguing about such line-drawing — and seem to vastly prefer it to hashing out our disputes on substance. Perhaps that's because arguing on substance is only fruitful when the different sides share a few common premises — and the different sides in our many disputes increasingly share no relevant principles at all.

If productive argument is a give-and-take that ends with some kind of meeting of the minds, arguing about transgression of moral lines is more like zero-sum warfare, a battle for supremacy, in which territory is conquered and enemies are banished. The point is less to convince your opponent that she has made an error of reasoning or is wrong on the facts as to convince your own side, as well as the dwindling crowd of ostensibly neutral observers on the sidelines, that they are excused from having to take your opponent seriously because she has crossed a line beyond which people shouldn't be granted a hearing.

This dynamic plays out more and more in our public arguments. The fights Rep. Ilhan Omar (D-Minn.) keeps igniting over Israel and Jewish influence in Washington take this form every time. Omar tends not to criticize specific policies of the U.S. or Israel on the merits, calling them contrary to the American national interest or needlessly cruel to Palestinians. Instead, she claims that those on the other side of those questions wish to silence her and that they are motivated to take their positions out of dual loyalty or the malign influence of well-heeled lobbyists working to advance Israel's interests in Washington.

This is a second-order claim about moral lines. Omar wants to argue that those who disagree with her about American policy toward Israel are illegitimate, partly because they're dishonest, and partly because they treat her own views as illegitimate. Her critics then respond by confirming the latter point by trying to get her caucus in the House to denounce her for crossing another line, into anti-Semitic speech. At no point is Omar criticizing American policy, or her opponents defending it, on the merits. That's because they'd much rather scream variations of "You can't say that!" at each other.

But of course they wouldn't feel compelled to yell such things if they were true. The list of moral issues on which nearly all Americans can agree — and the corresponding list of things one is truly forbidden to say in public — grows shorter every day. The fact is that people can say pretty much anything they want in public as long as they're willing to brave a hail of verbal abuse from one faction or another. When they do so, they can usually seek and find support from another, allied faction.

America doesn't have a free speech problem. It has an intractable moral conflict problem.