I don't understand anti-semitism.

[Nonhlanhla]

20. It goes back to at least the beginning of Christian history

In the last decades of Second Temple Judaism, which was dominated by the Sadducee sect in Judaism and was centered around the Temple in Jerusalem, rival groups arose within Judaism, including the Pharisees and the Jesus Movement. The latter was actually theologically related to the Pharisees (Jesus was quite probably a Pharisee), and both groups wanted to reform Judaism, albeit with slightly different emphases. With the destruction of the Temple by the Romans in 70 CE, the reign of the Sadducees came to an end, and the Pharisees, which centered Judaism around the Torah and synagogue, rose to prominence within Judaism (this being the beginning of the rabbinic Judaism we still know today). Their main rival was the young Jesus movement, which, though arising out of Judaism and indeed also out of Pharisaism, had already begun to spill over into the pagan population due to its aggressive missionary impulse, thus expanding its base significantly. The two movements operated with rival interpretations of Judaism, and as such, although originally sibling religions, carried within them the seeds of future opposition. As Christianity grew into a larger religion and lost its awareness of its originally Jewish identity, its position of power of its smaller sibling religion eventually turned into outright animosity, especially since the essential point of difference was the status of Jesus (central to the church, rejected by Judaism), and Christian anti-semitism was born. Over the centuries Christian treatment of Jews became worse and worse, complete with horrible stereotypes of Jews. This, as we know, eventually culminated in the Holocaust, which has muted anti-semitism for a few decades. But the roots of it are still there, including its roots in Christian theology. And this means that it tends to pop back up. It is essentially irrational, but it is deeply rooted in Western culture.

I recommend Daniel Boyarin's writing on Christian origins. There are also scholars who suggest that anti-semitism go back to even before Christian times in the Roman Empire, and that this influenced Christianity once it became a primarily Roman religion.