In 1979 The Progressive, a monthly journal that is both liberal and libertarian (an infrequent combination) endured the longest prior restraint in American history -- six months and 19 days. The U.S. government had convinced a federal court to prevent the publication of an article "The H-Bomb Secret: How We Got It, Why We're Telling It."

The rest of the press was divided in its response to this act of censorship for alleged reasons of national security. Some newspapers urged The Progressive to back down because, The Washington Post said, the case was "a real First Amendment loser." But the editor of The Progressive, Erwin Knoll, is stubborn. He also turned out to be right. Eventually, the government slunk away as it became clear that the beleaguered article had contained no classified information at all and was being published precisely to show, as Knoll put it, "how much unnecessary secrecy is being maintained in the name of national security."

A year later, Knoll was hit with another hailstorm of criticism, this time from his readers. He is pro-choice, and that is the editorial policy of The Progressive, but he thought it would be challenging for his readers to be exposed to the crisp, lucid views of a longtime writer on civil rights, Mary Meehan, who is pro-life. Well, as the sulfurous letters, from apoplectic liberals poured in, you would have thought Knoll had written an editorial endorsing Roy Cohn for the Supreme Court. Subscriptions were cancelled, and anathemas were hurled. In another time, Meehan and Knoll might have been stoned.

This year, some readers of The Progressive have been infuriated by an ad showing a black man, a white woman and a middle-aged white man -- all members of a union local in the tobacco industry. The message was that if you quit smoking, you're going to threaten the livelihoods of thousands of people like the Norman Rockwell-style trio in the ad.

The Progressive has relentlessly attacked the tobacco industry's lobbying efforts for its poison, but Knoll figured that his readers are not so pliable that they have to be shielded from this pitch. Like one-time editor Benjamin Franklin, Knoll is aware that a magazine is not a public stagecoach that has to take every passenger. But the editor also doesn't have to agree with every passenger he lets on.

The most recent confrontation between Knoll and some of his liberal (but not libertarian) readers has been over a small ad placed by Feminists for Life of America. It shows an eight-week-old fetus and suggests she may need protection from being killed. One deeply offended reader asked in the letters column: "What's next -- American Nazi Party advertising? The Ku Klux Klan? I thought I was subscribing to The Progressive."

More ominous, in view of the chronic financial problems of The Progressive, was a letter from June Makela, executive director of Funding Exchange, a conduit of financial aid for various enterprises devoted to social change. The executive director wrote Erwin Knoll that "we were greatly offended by your decision to run such an advertisement. Although we respect the integrity of your magazine in setting its own policies, we are surprised and shocked over the apparent lack therein with regard to advertisements.

"The staff of Funding Exchange has decided not to renew its subscription, and I am afraid that this inconsistency will also make it difficult for our staff to lobby for funding for your publication."

In answering, Erwin Knoll said: ". . . You find it intolerable that The Progressive's readers should be exposed to a point of view you deem obnoxious. We have more confidence than that in our subscribers . . . we believe we can expose them to any thought without jeopardizing their minds, their bodies or their immortal souls. . . ."

Also excoriating the magazine for imposing an eight- week-old fetus on its more sensitive readers was Michael Ratner, an attorney for the Center for Constitutional Rights in New York. "Happily," Ratner wrote, "I am not a subscriber so I needn't cancel my subscription. I would surely do so after seeing the anti-abortion ad of the Feminists for Life of America."

Knoll, a kindly man, responded with sympathy: "I'm sorry that you had no subscription to The Progressive just when you needed to cancel one. It's a good idea to subscribe so that you won't be caught in that sort of predicament."

Years ago, Phil Kerby, who recently retired as an editorial writer for the Los Angeles Times, sent me an apothegm that ought to have been in George Seldes' splendid anthology, "The Great Thoughts." Said Kerby: "Censorship is the strongest drive in human nature. Sex is only a weak second."