EVERY year the Costume Institute of the Metropolitan Museum of Art hosts a gala. A single ticket costs $30,000. New York’s A-listers and wannabes deck themselves in overwrought garments designed for the party’s theme. Three years ago “China: Through the Looking Glass” inspired dresses with dragons (pictured), hair held in place with chopsticks and, from a few sartorially confused celebrities, kimonos.

The attire prompted an outcry over “cultural appropriation”—an elastic, ill-defined gripe. No such furore arose over the outfits at this year’s gala, “Heavenly Bodies: Fashion and the Catholic Imagination”, even though they included a stilettoed and sequinned pope, Jesus Christ in a gold tiara, and a spectacularly winged angel. Why not?

It is not as though the concept of cultural appropriation has fallen out of use. Gonzaga University issued a firmly worded statement warning “non-Mexican individuals” against celebrating Cinco de Mayo; the campus multicultural centre published a minatory infographic ordering, “Don’t you dare try on that ‘sombrero’.” About a week earlier an 18-year-old white student in Utah received hundreds of hostile comments after she wore a Chinese-inspired dress to her school prom.

The accusation is great at stirring up Twitter outrage. But what is cultural appropriation?

There is no agreed definition. Generally speaking, it’s the idea that a “dominant culture” wearing or using things from a “minority culture”—say, white American college kids in Brazilian bombachas or baggy trousers—is inherently disrespectful because the objects are taken out of their native context. 

It’s not a completely new idea. More than two centuries ago it was popular for upper-class British and French to have their portraits painted dressed as Turkish sultans, which the historian Edward Said called “orientalism”. More recently some black Americans griped when Elvis Presley filched classic rhythm-and-blues riffs and sold them back to white, mainstream society.

Yet today the idea has expanded to new extremes—and obstructs free expression. In American colleges and universities, a vocal minority of students are pushing for official policies banning the practice—by, for example, disciplining students who wear Halloween costumes deemed inappropriate.

The threat here is quite overt. Offence is inherently subjective; university bureaucrats should not punish one student simply because her clothes hurt the feelings of another. Beyond the threat of punishment lies the threat of social stigma—that students, fearful of being accused, will censor themselves or feel themselves censored.

Had the Met gala opted for an Islamic theme (say, “Arabian Nights: Magic and Islam”), accusations of appropriation would have surely followed. This year Jared Leto, an actor, dressed as Jesus; had he dressed as Muhammad, even if in a plain and historically accurate thobe and turban, he would provoke all manner of disgust and denunciation. One can conjure any number of nightmare scenarios for galas themed around Judaism, blackness or, say, Aztecs—none of whom remain alive to be offended—no matter how sartorially sensitive the dresses.

That is because cultural appropriation is less about cultural disrespect or intolerance—for which much clearer terminology already exists—than about reinforcing the oppressor-oppressed binary through which social-justice advocates see the world. Because Christians and whites are groups deemed to have power, all manner of borrowing or parody is intolerable. And the inverse gets a free pass: nobody is upset when Asians wear European clothes, for instance.

The remedy for the selective application of the cultural appropriation label is not its expansion—as this would sweep in all manner of innocuous social interactions—but its retirement. The phrase stigmatises the beneficial cultural exchanges that happen in art, music, dance, cooking and language. The very idea is self-defeating. To declare black culture off-limits to non-blacks, for example, is to segregate it.

The term also fundamentally misunderstands the process by which all cultures form and progress: through creolisation and intermixing. To appropriate the words of John Donne, no culture is an island entirely of itself.