Even the most ardent defenders of free speech — and we count ourselves among them —understand that a decent society requires some restrictions on what people can say. You can’t go on TV and call your neighbor a murderer if he is not, in fact, a murderer. You can’t call your ex-wife up in the middle of the night and whisper threats into the phone. You can’t shout “FIRE!” in a crowded theater. Or at least you couldn’t back when there were crowds and theaters, and before everything was on fire.

So we appreciate the motivation behind SEPTA’s prohibition on “political” advertising, which was struck down last week by a federal court. The transit agency put the ban in place in 2015 after receiving blowback for running an ad submitted by an anti-Muslim group, claiming that “Jew Hatred” is “in the Quran.” Who wants to look at something that hateful while riding down Broad Street?

But SEPTA ran into trouble when it recently refused an ad calling attention to racial disparities in home loans, from the Center for Investigative Reporting, calling it too political. The center filed suit, backed by the American Civil Liberties Union, claiming that SEPTA was infringing on its right to free speech, and the court found that SEPTA was unable to articulate clear, consistent standards for what ads it considered political in nature. This introduced the possibility that SEPTA, a government agency, could end up picking and choosing which messages could air in a public forum based on viewpoint, in violation of the First Amendment. Hence the decision that SEPTA must change its policy — the third such decision since 2015.

People celebrating this decision because they support CIR’s message ought to be clear-eyed about the fact that the door is now potentially swung open for ads they find objectionable as well. But it is more important to preserve the principle that state regulations of speech should be content-neutral than it is to kibosh any one ad, however heinous.

As for SEPTA, the transit agency doesn’t necessarily have to figure this out. It only needs to do so if it wants to preserve approximately $16 million in revenue it makes each year selling ad space on its vehicles and properties. We understand this is a lot of money for a cash-strapped agency. But the fact is that transit agencies across the country have repeatedly found themselves in court defending their ad policies: New York City, Seattle, Pittsburgh, Washington, D.C. It’s just very difficult to sell ad space, avoid offensive messages, and meet a government agency’s First Amendment responsibilities, all at the same time.

Nor would we expect the agency to find a simple solution in banning political ads and defining the term more clearly. We live in an era when the president endorses bean brands and opposes sports leagues. Will SEPTA then be expected to refuse ads from Goya or the Sixers? Isn’t capitalism itself a hot-button political issue these days? There are trade-offs to be made when you sell access to a public forum, and SEPTA may have to choose between more ads it doesn’t want or no ads at all.