Correction: An earlier version of this piece misidentified Superman as a caped crusader. He was the man of tomorrow, while Batman was the caped crusader.

Recent shootings — from the attempted attack on congregants observing Yom Kippur at a synagogue in Halle, Germany, in October, to the killing of 51 worshipers at two mosques in Christchurch, New Zealand, six months ago — have been tied to the promotion of anti-Semitism, Islamophobia and hate-fueled violence on the Internet. When far-right extremism goes viral online, the contagion infects flesh-and-blood human beings capable of materializing their hate by force.

So what do we do?

While restricting Internet hate speech is important, we might also consider devising a counterattack. Almost a century ago, when Jewish advocacy groups confronted the spread of fascist propaganda in the United States, they cooperated with other organizations and American mass media to produce counterpropaganda. This history shows that when social activists and media industry professionals join forces, they can mount a formidable challenge to the toxic rhetoric of the far right.

American anti-Semitism reached an apogee in the 1930s, spurred by the radio diatribes of the known anti-Semite Father Charles Coughlin and the scapegoating of Jews for the Great Depression. In response, the American Jewish Committee (AJC) established the Survey Committee, made up of professionals in fields including advertising, Hollywood filmmaking, broadcasting and academia. Its objective was to monitor the dissemination of anti-Semitic propaganda in the United States. Under advertising executive Richard Rothschild’s direction, the Survey Committee also mounted a counterattack, producing what historian Stuart Svonkin calls “propaganda against prejudice.”

The Survey Committee quickly evolved into a complex web of interconnected committees, divisions and sections. The Film Section advised Hollywood studios to ensure their films didn’t inadvertently perpetuate Jewish stereotypes. The Magazine Section placed news items and editorials about the harmful effects of prejudice in some of the nation’s most popular publications. And the Mass Media Education Committee, made up of powerful executives from the advertising and entertainment industries, met regularly to discuss new ways of using media to curb social biases.

The head of the Radio-Television Section was Milton Krents. Newly hired at the AJC, Krents stood before a map of the United States and, like a general positioning troops on the battlefield, used pin tacks to identify radio stations. “Today, Nazi Germany is waging a new kind of war,” he wrote in an essay for the Contemporary Jewish Record (the predecessor to Commentary magazine). “In place of the shock troops of the first World War are giant radio transmitters firing their invisible salvos of subversive ideas in a never-ceasing barrage.” For Krents, propaganda was as powerful as artillery fire.

A bevy of media theories and tactics emerged from the AJC’s work. Each had a unique name, usually dreamed up by either Rothschild or Krents.

“Quarantine” was Rothschild’s term for relegating anti-Semitic smears to the margins of public discourse. The goal was to avoid inadvertently publicizing Nazi invective. In the essay “Are American Jews Falling Into the Nazi Trap?” Rothschild wrote that when the Germans claimed their objective was to safeguard civilization from the Jews, American Jews shouldn’t contest the point; that would only serve to spread the lie. Instead, they should flip the script by characterizing the Nazis as the threat. Then they should identify their cause as America’s cause and show that America represents the forces of good.

Another strategy, coined by Krentz, was “salting in,” or sprinkling positive messages into popular programming. Krents preferred this method to producing original anti-prejudice broadcasts, arguing that when messages are “salted in,” they are less likely to “boomerang,” or be rejected by the public as Jewish propaganda.

Krents “salted in” socially liberal messages on the “Uncle Don” radio show, a popular children’s program that reached millions of young listeners over station WOR in New York. The Mass Media Division helped develop “Superman” story lines that pitted the man of tomorrow against the forces of fascism, both foreign and domestic. The committee even created new series, such as the 1942 radio show “Dear Adolf,” in which archetypal Americans read letters to the Führer and pledged their support to overcome leaders who would, as James Cagney declared, “set class against class, whites against negroes, Christians against Jews. And we know they’re playing Adolph’s game — and we’re onto them.”

The AJC didn’t mount its counterpropaganda campaign alone. There were many civic organizations, defense leagues and civil rights associations engaged in the fight. Spurred by the rise of the Nazi propaganda machine, these groups marshaled the power of American mass media to fight extremism.

After the war, they continued to operate as a united front, fighting not just anti-Semitism but “prejudice,” a purposely broad term identifying the common enemy of America’s diverse racial, ethnic and religious groups. As part of this effort, the AJC helped produce “The Challenge,” a hybrid film noir/informational film dramatizing the 1947 report issued by the President’s Committee on Civil Rights. In the 1950s and 1960s, the AJC presented anti-prejudice TV specials that aired on the “Big Three” networks — NBC, CBS and ABC — reaching as many as 7 million viewers in a single evening.

But propaganda against prejudice soon declined. Liberal Cold Warriors became increasingly distrustful of mass culture, and they argued that media campaigns weren’t the best way to curb biases among the American public. Instead, they advocated sending speakers to Rotary Club meetings and gatherings of the local Women’s Auxiliary Committee. The idea was that these groups could then spread the AJC’s anti-prejudice message to their family, friends and neighbors through their civic work. In an era of interest group pluralism, grass-roots engagement with community organizations gained favor.

The AJC’s messaging campaign wasn’t perfect. Like many liberals of the era, Rothschild and Krents thought inequality stemmed from prejudice. Change hearts and minds, they believed, and a more just world would follow. Because of this assumption, their work did nothing to tackle systemic problems, like discriminatory housing policies or racist hiring practices.

But some of their ideas are worth revisiting today as we grapple with extremism in the media. When Jacinda Ardern, the prime minister of New Zealand, refused to say the name of the Christchurch shooter before the news media, she was implementing the strategy of quarantine. When Web hosting and Internet security providers denied services to 8chan and Gab, temporarily shutting down these sites, which hatemongers have used as platforms, the noxious rhetoric of the far right was somewhat contained.

If today’s media industry professionals — from social media chief executives to TV writers to celebrities to online advertisers — want to stem the tide of extremism online and across culture, they should coordinate with advocacy groups on the model developed by the AJC, not only working to contain incendiary speech but also producing counterpropaganda against hate.

Today’s media landscape is dramatically different from that of the mid-20th century, but the problems we confront now are also frighteningly familiar and enduring. As racism and bigotry online continue to inspire acts of bloodshed, looking to the past for answers becomes more urgent. We don’t have time to lose.