I think that the first persecution of a Jew was when King Nimrod threw Abraham into the fiery furnace because Abraham refused to adapt his belief in Monotheism to Nimrod's pagan view. From that moment on there has been a continual struggle between the believers in God and His absolute Unity on the one side and the believers of division and Paganism on the other. According to this it transpires that "anti-Judaism" was sparked off by the actions of one man and actually pre-dates the Jewish Nation by hundreds of years.
What is indisputable is that there are many different forms of Jew hatred and many different reasons behind them. However, I think that anti-semitism is unique for a few reasons it is universal - i.e. it is found amongst Pagans, Christians, Moslems, Enlightenment, the Left and the Right. Because it is so intense - i.e. the various attempts at total annihilation, unspeakable torture, etc. The sheer fact of its Longevity, it was found in Egypt, Greece, Rome, Dark and Middle Ages, the Renaissance and up to and including modern times. There is no rationality to its claims. For example, deicide, the blood libel, the exaggerated influence of the Jews, Protocols, the anti-semitic attacks are often against best economic and scientific interests.
One of the possible problems is that of an ideological clash. Judaism has never been secretive about its condemnation of any deviations from absolute, pure monotheism. Its condemnation of idolatry, deification of humans and deviation from the Bible in any form. This has incurred us a lot of hatred as well. Regarding Christian antisemitism, (see God's First Love, Heyer. Faith and Fratricide by Rosemary Reuther) there are a number of other factors as well. The Christians claim to have the Jewish messiah, yet the Jews who originated the idea, believed in it and expected it - rejected Jesus as a candidate! The Christians claim that the Jews killed Jesus - even though crucifixion was not a Jewish method of execution and even though the Jewish courts had no power to judge capital matters at the time. They also claim that it is impossible to keep Jewish law, and that Jesus made it obsolete - the existence of Jews to this day, despite persecution etc. who still keep Jewish law is a contradiction to that belief.
There is also a tremendous sense of self-righteous anger - the Jews have resisted every effort to convert them whether it was the Crusades, the Inquisition or missionaries. Jealousy - Jews have the original language of the Bible, the traditions of the Bible and the Land of the Bible - the Christians took their Bible from us, the Psalms from us, their Messiah from us -and therefore they resent us and are jealous.
I suggest an excellent book on the subject called "Why the Jews? by Joseph Telushkin and Dennis Prager.
