score:6
Antisemitism is something that is quite unbelievable for us nowadays
You must be living in a cave paradise.
Indeed, right after WW2 antisemitism became quite unpopular in Europe, mostly because
However, antisemitism did not disappear, it is just names its targets differently (Rootless cosmopolitans, Zionists).
The roots of antisemitism are simple - xenophobia is a normal (i.e., common) part of human psyche and it manifests itself in all sorts of bigotries. All minorities suffer from its consequences (e.g., Chinese in California 150 years ago as documented by Mark Twain).
When the hated minority is "invisible" (almost completely assimilated, like the Jews in Germany 100 years ago), the bigotry can feed conspiracy theories and become much more vicious.
The only part of Nazi antisemitism which was unprecedented was the scale, i.e., applying the full power of 20th century industry to the task of exterminating people (Jews, Gypsies, h*m*sexuals &c). The racial laws were not particularly exotic by world standards (cf. Dhimmi).