Daniel Lubetzky

TEL AVIV — THREE weeks ago, my father was riding on a public bus in Jerusalem’s Armon Hanatziv neighborhood when terrorists from East Jerusalem shot him in the head and stabbed him multiple times. Afterward, as he lay unconscious in the intensive care unit of Hadassah Hospital in Jerusalem, fighting for his life, one question was on my mind: What inspired the two young Palestinian men to savagely attack my father and a busload of passengers?

My father, Richard Lakin, dedicated his life to the cause of Israeli-Arab reconciliation. Ever since moving to Israel from Connecticut in the 1980s, he spent his career teaching English to Israeli and Arab children. Inspired by his experience marching with the Rev. Dr. Martin Luther King Jr. in the 1960s, he became a founding member of Israel Loves Iran, a social media initiative designed to bring the citizens of these two nations closer together. When news of his tragedy broke, many of the Christian, Muslim and Jewish residents of Jerusalem who knew my father and admired his work rushed to his bedside to pay their respects and say a prayer for his recovery. Even Ban Ki-moon, the secretary general of the United Nations, stopped by on his recent visit to Israel.

Watching the well-wishers congregating in the intensive care unit, however, I realized that the world leaders who were having the most impact on the situation in the Middle East right now weren’t Mr. Ban or Prime Minister Benjamin Netanyahu, but Mark Zuckerberg of Facebook, Jack Dorsey of Twitter and other young entrepreneurs who shape the social media platforms most of us use every day.

It may sound strange to talk of Twitter and Facebook as relevant players in the war against terror, but as the recent wave of violence in Israel has proved, that is increasingly the case. The young men who boarded the bus that day intent on murdering my 76-year-old father did not make their decision in a vacuum. One was a regular on Facebook, where he had already posted a “will for any martyr.” Very likely, they made use of one of the thousands of posts, manuals and instructional videos circulating in Palestinian society these last few weeks, like the image, shared by thousands on Facebook, showing an anatomical chart of the human body with advice on where to stab for maximal damage.

Sickeningly, my father, too, became a viral hit on Palestinian social media: Hours after he was shot and stabbed, a video re-enactment of the attack was posted online celebrating the gruesome incident, and calling on more young Palestinians to go out and murder Jews. Such images, YouTube videos and comments have become a regular feature on social media after every attack.

My father raised me to cherish and protect free speech, but the very liberty that free speech was designed to protect is at stake when it is used to spread venom and incite violence. Just as it is universally recognized that shouting fire in a crowded theater is dangerous and should be prohibited, so, too, must we now recognize that rampant online incitement is a danger that must be reckoned with immediately, before more innocent people end up as victims.

The companies who’ve turned social media platforms into very big business argue, and rightly so, that monitoring each post is nearly impossible, that permitting users the freedom of expression is essential, that there are already steps in place to combat hate speech. All that is true. But something new is happening today, and what Facebook, Twitter and the others must realize is that the question of incitement on social media isn’t just a logistical or financial question but, first and foremost, a moral one.

This wave of terrorism is different from anything we’ve seen, involving not terrorists recruited by shadowy organizations but ordinary young men and women inspired by hateful and bloody messages they see online to take matters and blades into their own hands. Just as many of us now argue that we should hold gun manufacturers responsible for the devastation brought about by their products, we should demand the same of social media platforms, now being used as sources of inspiration and instruction for murderers.

One immediate solution is to remove blatant incitement without waiting for formal complaints — it’s one thing to express a political opinion, even one that supports violent measures, and another to publish a how-to chart designed to train and recruit future terrorists. To that end, an Israeli nonprofit took legal actionagainst Facebook earlier this week, demanding that the company do more to monitor and remove unacceptable content. My family joined the lawsuit as plaintiffs. Still, I believe that any truly successful effort to curb the culture of hate on social media must come from the companies themselves.

Companies can become more active in combating hate. The popular social networking site Reddit, for example, not only banned specific types of unacceptable content — such as a group encouraging rape — but it also engaged specific user groups in dialogue, a simple act of civility that succeeded in curbing the worst rhetoric. Companies can and must work harder — using all the tools at their disposal — to create an online culture that does not tolerate violence and hate.

Sadly, for my father, it’s too late: Two weeks after the attack, he succumbed to his wounds. When they heard the news of his passing, many of his friends — Christians, Muslims, Jews — posted his favorite photo on their social media channels. It shows an Arab and an Israeli boy, their arms around each other, while the text around them spells simply “coexist.”