Suspicion of the mainstream media is commonplace on the right, but that long-standing worry now extends to social media. Conservatives widely believe, despite minimal evidence, that the big social media platforms are censoring their voices via “shadow banning” or algorithmic bias. In response, President Trump has repeatedly called for the repeal of Section 230 of the Communications Decency Act, an obscure law that fundamentally shaped the nature of the Internet in the 1990s.

Section 230 shields social media companies from liability for user-posted content. It is rooted in a body of jurisprudence protecting freedom of speech for bookstores. One could sue an individual author for defamation but couldn’t hold the bookstore owner who sold the book liable, ultimately allowing owners to carry controversial books if they chose to do so. Section 230 extended this principle to the Internet, giving platforms control over user-posted content without having to worry about lawsuits. This kept the Internet from turning into a web of either tightly controlled walled gardens that banned all controversial content or unmoderated sites that banned none at all.

Trump and allies such as Sens. Marsha Blackburn (R-Tenn.) and Josh Hawley (R-Mo.) — both of whom have proposed legislation that would condition Section 230 protections on not discriminating against conservative content — may care little about this history. But they should.

While trying to force media to be “fair” sounds good in theory, waging political campaigns via regulatory policies can backfire. In fact, the last time the federal government attempted such a project, the result was the most successful episode of government censorship of the last half-century and it was conservatives who were the primary target.

The Fairness Doctrine certainly sounded like a good idea to media reformers in the late 1940s and 1950s. Because of the scarcity of stations, the Federal Communications Commission mandated that television and radio station owners give airtime to both sides of any controversial issue, like school desegregation, to ensure that the public would have access to all points of view.

In practice, however, it was a potential weapon waiting for the right set of unscrupulous political operatives willing to wield it. After all, the FCC, an agency filled with executive appointees, decided whether stations fulfilled this requirement and also controlled whether stations’ licenses would be renewed. In other words, the president could game the Fairness Doctrine by appointing political allies to the FCC and then leaning on them to privilege or punish particular content. And that is precisely what John F. Kennedy did in the early 1960s. Kennedy had narrowly won the election of 1960; his campaign had nearly foundered in the West Virginia Democratic primary because of what one staffer called “every hatemonger, radio preacher and backwoods evangelist” who attacked Kennedy’s Catholic faith and liberal policies. The most prominent of these radio preachers was a fundamentalist, Presbyterian minister in New Jersey named Carl McIntire, who had an estimated weekly audience of 20 million listeners. (For the sake of comparison, that matches Rush Limbaugh’s peak some 40 years later.)