When left unchecked, anti-Semitism enables prejudice and active discrimination against multiple communities within societies | Ina Fassbender/AFP via Getty Images Leon Saltiel is the World Jewish Congress representative at U.N. Geneva and UNESCO, and its coordinator on countering antisemitism. His most recent award-winning book is “The Holocaust in Thessaloniki: Reactions to the Anti-Jewish Persecution, 1942–1943.” As Sweden prepares to host this week’s meeting of the International Holocaust Remembrance Alliance (IHRA), I find myself grappling daily with how anti-Semitism still thrives, some eight decades after the end of World War II. I routinely think about this ongoing enigma as part of...