Ironically enough, 1st century Jewish sectarianism gave birth to antisemitism in a clear ideological way. With the rise of Christianity and Gnosticism, both had their origins in Judaism and both were polemical towards other Jewish groups as were other Jewish groups polemical towards them such as the Pharisees (and of course the Pharisees were very polemical towards other groups, just look at Rabbinical writings about the Sadducees, and consequently the Sadducees were also polemical). While early Christianity and Pharisaism (transitioning into Rabbinical Judaism) fought for the control of Judaism as a religion like twins in the womb as Jacob and Esau were (with Christianity eventually going it's own way in the 2nd century and Pharisaism becoming Rabbinic Judaism in the 2nd century following the Bar Kokbah revolt) Gnosticism was busy being the first case of metaphysical antisemitism that conflicted with both Rabbinic and Christian theology regarding the Hebrew scriptures. Essenic polemics from the 3rd century BC to the 1st century AD were somewhat similar to Christian polemics as both groups were in opposition to the Temple in Jerusalem since they believe it was spiritually unpure and not in proper accords with the laws of the Hebrew scriptures.
Ultimately, Second Temple sectarianism between all Jewish groups, Pharisees, Sadducees, Essenes, Baptists (of John), Christians, Zealots, seems to have had long lasting effects and ironically produced antisemitism, at least the kind that we saw in Europe during the middle ages.
But the antisemitism espoused by Nazis in the 20th century was a different kind of antisemitism from the kind of the Inquisition, for even though both were targeting race, they were doing it for very different reasons, as the inquisitors were not so much concerned with the actual genetics/ethnicity of the New Christians as they were with their religious practices (Crypto-Judaism) since Christianity is not an inherently racist religion. Nazism actually is inherently racist and did do it purely based off of who Jews were as a people with little or no concern for the actual Jewish religion.
Yet of course Nazis were heavily inspired by the antisemitism of the past from Christians of the likes of Martin Luther and St. John Chrysostom, even if that antisemitism was different from theirs. It could be said that Nazi antisemitism is really just a more extreme derivative of Christian antisemitism, where it's roots lay (that is, in extreme German Protestantism and Catholicism transitioning into Nationalism just before, during, and after WW1), but with the state replacing God, and yet we see how easily the average Christian can settle into this proving the antecedents remarks, for although Nazism in itself is not compatible with Christianity, the Christian masses can be enticed into it.
Antisemitism is Jewish.