The Racial Theory
Maybe Jews have been hated because they are a different race.
The overriding problem with this theory is that it is self-contradictory: Jews are not a race. Anyone can become a Jew and members of every race, creed and color in the world have done so at one time or another.
There is no distinguishing racial physical feature common only to Jews. Even the idea of a "Jewish nose" is a myth. (A study done in 1911 disproved the "existence of the Jewish nose.") Anti-Semites dont hate only those Jews who have distinctively Jewish physical features; they hate all Jews.
They hate Eastern European Jews; they hate Israeli, Russian and Yemenite Jews; they hate blond, blue-eyed Dutch Jews as well as dark-skinned, Mediterranean-looking Jews. Any Jew will do.
Anti-Semitism cannot be explained as racism for the very simple reason that Jews are not a race.