Per #IsaacAsimov in #DarkAges, European #antiSemitism began in earnest with the #Visigoths as a result of post-#Arian conversion politics on the Iberian peninsula.
The extremism they developed remained a Spanish heritage right down into modern times.
Religious tolerance, once established, was usually extended to Jewish people, as well.
Visigothic kings initiated a policy of brutal anti-Semitism, which has stained #Christian Europe ever since.
