On the first night of Hanukkah, two gunmen opened fire on Jewish families celebrating at Bondi Beach. Sixteen people are dead. Among them were Rabbi Eli Schlanger, who organized the celebration; Alex Kleytman, a Holocaust survivor killed while shielding his wife; a 12-year-old girl; and others ranging in age from 10 to 87. This was not spontaneous violence. It was the foreseeable outcome of a climate in which antisemitism has been tolerated, rationalized and normalized. How can we continue to tolerate such hate? Violence against Jews becomes possible long before the first shot is fired — when Jews are isolated,...