For one thing, their cultural homeland is comparatively desirable real estate in that region, (that's why they conquered it after the whole Egypt thing) so they were always getting conquered. When they were conquered, they got angry and revolty about it, because hey, you would too if someone invaded your hard-earned home and started messing with your stuff. That made the conquerors dislike them, and they spread nasty stories about "them uppity judeans."

When they were forced into diaspora, most people in other places were not too fond of strange foreigners moving in next door, singing songs at all hours of the night and cutting the skins off babies' penises and committing the sin of usury. (AKA modern banking.). So more nasty stories were spread.

For much of the last 1500 years or so they were also seen as the cause of the death of Jesus, which is a BS reason to hate someone, seeing as Jesus was supposed to be crucified anyway to become the messiah and whatnot.

Correct me if I'm wrong on any point.