Antisemitism: What is the root? The high-profile incidents allegedly perpetrated by radicalized Islamists at two synagogues, a school, and elsewhere have captured attention. But Binyomin Jacobs, a revered leading European rabbi based in the Netherlands who served for years on the board of the Cheder Orthodox Jewish school in Amsterdam that was recently attacked, said the underlying issue is rooted in the general populace’s tolerance and participation in “smaller” acts of antisemitism in everyday life. In Jacobs’s view, a type of mob mentality is forming against Jews in Europe, driven in part by rage against the state of Israel. Actions...