What the world should already know but so often forgets is that Jews are the canary in the coal mine of civilization. Anti-Semitism is like cancer; unchecked, it can metastasize and sicken the entire body. When civilized nations fail to rise up against the Jew-haters in their midst, it is often just a matter of time before the Jew-haters in their midst rise up against them.
Read the whole thing. (Via Volokh, where Randy Barnett has further thoughts.)