After the attack in Manchester last Yom Kippur, at the Heaton Park Hebrew Congregation, this should have been a moment of reckoning. Instead, it is yet another warning. The question is no longer whether antisemitism is escalating into violence. The question is how many such warnings and how many acts of egregiously violent terrorism are required before that reality is confronted. Not all warnings arrive in flames. In London and Edinburgh, among other major cities, Jewish people have been advised by police to remove their yarmulkes and conceal their Star of David necklaces so as not to “trigger” pro-Palestinian protesters...