A candlelight vigil for victims of the shooting at the Congregation Chabad synagogue in PowayJohn Gastaldo / Reuters

In my neighborhood, there are a number of synagogues and churches. The church doors are open, welcoming all. The synagogues have armed guards, fences, door codes, and people who will stop strangers as they enter. Ostensibly these are welcomers, but their real job is to check whether these strangers wish to do the people inside harm. Our children look at the church across the street and recognize that, while Jews need protection, the kids there do not.

The attack on a Chabad synagogue in Poway, California, has reminded Jews—yet again—that their houses of prayer are not safe spaces. But for the fact that the assailant’s gun jammed, the attack could have been far worse than the October attack in Pittsburgh, which claimed 11 lives.

In the wake of the Poway attack, law-enforcement officers, government officials, and the media kept stressing that the gunman had acted alone. They may have been trying to reassure the public, and in the narrowest technical terms, they may have been correct.

But this assailant was no lone wolf. He is part of a nexus of haters. The shooters in Charleston, Pittsburgh, Christchurch, and now Poway all relied on similar language and memes. The Christchurch and Poway shooters both posted manifestos prior to their rampages. They referred their social-media followers to some of the same websites and offered similar justifications for their actions.

These gunmen may not have received direct orders from a leader, but social media have eliminated the necessity for a leader to issue orders, facilitating their radicalization. And though there is no reason to think they’ve ever met, they are deeply connected, one with the other.

White supremacism—which has at its core anti-Semitism—is nurtured by the extremist rhetoric that has become almost commonplace within the United States. It is growing and flourishing. Had this act of terror been committed by an individual influenced by ISIS or al-Qaeda, it would quickly have been labeled terrorism. Government agencies must recognize white-supremacist attacks as a form of domestic terrorism, and treat them as such.

Our president’s claim that these attacks are coming from a “small group of people” and present no “rising threat” is contradicted not only by Charleston, Poway, and Pittsburgh, but also by recent assessments by law-enforcement entities. Both the FBI and the Department of Homeland Security have warned of the threat of violence from white supremacists. In recent years, white supremacists have been responsible for more homicides than any other extremist group.

The federal government needs enhanced powers to regularly assess and share data on the activities of these individuals and groups. Federal law-enforcement agencies must be empowered to regularly assess this threat and train officers on how to address it.

But anti-Semitism itself is an equal-opportunity hatred, even if the violence it sparks is not evenly distributed. It also comes from the political left. On my own campus, a pro-Palestinian group recently called for the boycott of all Jewish groups, including Hillel and Chabad. That’s anti-Semitism.

In truth, when it comes to anti-Semitism, the right and the left often find common ground. The far right talks about the federal government as ZOG, the Zionist Occupation Government; the left sees AIPAC, the American Israel Public Affairs Committee, as a behemoth of unbelievable proportions, driving American policy in ways that are antithetical to America’s best interests. This absence of a dividing line between left and right when it comes to anti-Semitism was evident when the former Ku Klux Klan leader David Duke clicked “like” on Representative Ilhan Omar’s tweet claiming that American support of Israel is “all about the Benjamins baby.”

How can this hatred find such hospitable circumstance at diametrically opposed ends of the spectrum? Part of the answer lies in the ubiquitous nature of anti-Semitism. Jew hatred can best be compared to a herpes virus for which there is no cure. It is adaptable and thrives in a welcome environment. Anti-Semitism flourishes when anti-Semites feel emboldened and think that what they are doing will be welcomed and not looked upon askance. That is true of people on the right and the left.

Certainly the government must act, but in the interim, what can we as individuals do? Though it sounds prosaic, we must speak out against the rhetoric that gives rise to and eventually legitimizes such acts of hate. We must shame people who, though they may never, ever contemplate acting on their hate and prejudices, express Jew hatred. And, above all, we must be willing to criticize—directly and not gingerly—our political allies when they cross the line into anti-Semitism.

Acts of terror never begin with actions. They begin with words. We must place this kind of talk well outside the pale of legitimate discourse. There is nothing fine or legitimate about these views.

For the past seven decades, it has been shameful to be an open anti-Semite. We assumed that, after the Holocaust, the world recognized where anti-Semitic rhetoric can lead. We were wrong.

We must strive to banish open anti-Semitism so that we will no longer need armed guards screening worshippers as they enter their synagogues.

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