Jealousy plays a part, the closed nature of some sects is another. A now-deceased Jewish colleague had a son who has publicly dissed me for being a "bad Jew," because he has decided I'm Jewish (go figure--I look the part to him, ergo sum) and won't observe their traditions (whatever floats his boat).
The "really existing Socialism," or "East Germany," as we called it, claimed that their territory had been cleansed of Nazis after the War, and so never ever needed any de-nazification programs for their part of Germany. The West alone owned their shame, and publicly made efforts to educate their people for a "never again" generation. So there are several generations of Eastern Germans who were never taught that their grandparents were involved in some REALLY evil activities on their soil. Guess where the most concentrated areas of anti-Jewish activity are today? Half (or more) of these people have never even met a Jew. I figure it must be something like haters of Mexicans in Idaho.
I'm sure there are parts of Germany where it would be prudent to not wear a skull cap. There are FAR more such neighborhoods in London, Paris, Brussels or probably even Montgomery or Waco.
The fact that this particular hatred has continued for so many centuries is what fascinates me. Two thousand years ago, the Egyptians and the Romans, five hundred years ago, the "Catholic Kings" of Spain, 100 years ago, the "National Socialists." In all that time, not one king or major monarch has been a Jew. Indeed, if the NSDAP hadn't had their sights on the Jews, a certain Albert Einstein might have helped Hitler get the atomic bomb way before we did. Hate is rarely rational or beneficial.