This tactic was used on the language of social justice, which was appropriated by opponents and redeployed nihilistically, in an open effort to sap its power while simultaneously taking advantage of what power it retained. Anti-racists were cast as the real racists. Progressives were cast as secretly regressive on their own terms. This was not a new tactic, but it was newly effective. It didn’t matter that its targets knew that it was a bad-faith maneuver, a clear bid for power rather than an attempt to engage or reason. The referees called foul, but nobody could hear them over the roar of the crowds. Or maybe they could, but realized that nobody could make them listen.

“Fake news” as shorthand will almost surely be returned upon the media tenfold. The fake news narrative, as widely understood and deployed, has already begun to encompass not just falsified, fabricated stories, but a wider swath of traditional media on Facebook and elsewhere. Fox News? Fake news. Mr. Trump’s misleading claims about Ford keeping jobs in America? Fake news. The entirety of hyperpartisan Facebook? Fake news. This wide formulation of “fake news” will be applied back to the traditional news media, which does not yet understand how threatened its ability is to declare things true, even when they are.

Facebook may try to address the narrow version of the problem, the clearly fabricated posts. Facebook has plenty of tools at its disposal and has already promised to use one, to bar sites that have been flagged as promoting falsified content from using its advertising platform. But the worst identified defenders make their money outside Facebook anyway.

Another narrow response from Facebook could be to assert editorial control over external forces. Facebook tried this, to a very limited extent, with Trending Topics. Members of the company’s editorial staff wrote descriptions of trending news stories, accompanied by links they deemed credible. This initiative collapsed in a frenzy of bias accusations and political fear. But it is easy to imagine a system in which a story, upon reaching some high threshold of shares, or a source, upon reaching some cumulative audience, could be audited and declared unreliable. This could resemble Facebook’s short-lived experiment to tag satire articles as such.

A number of narrow measures could stop a fake story about the pope, for example. But where would that leave the rest of the media? Answered and rebutted, and barely better positioned against everything else that remained. It would be a still-dominant news environment in which almost everything there before remained intact, the main difference being that it would have all been declared, implicitly, not fake.

Facebook is a place where people construct and project identities to friends, family and peers. It is a marketplace in which news is valuable mainly to the extent that it serves those identities. It is a system built on ranking and vetting and voting, and yet one where negative inputs are scarcely possible, and where conflict is resolved with isolation. (Not that provisions for open conflict on a platform present any easy alternatives: For Twitter, it has been a source of constant crisis.)

Fake news operations are closely aligned with the experienced incentives of the Facebook economy — more closely, perhaps, than most of the organizations that are identifying them. Their removal will be an improvement. The outrage at their mere existence, and at their promotion on a platform with the stated goal of connecting the world, will have been justified.