Assuming that OP hasn't been around for thousands of years himself, I could only point out modern day antisemitism which makes perfect sense. OP never asked for a complete history.
However, if you're going to get to the root of things, you'd have to bring up religious prejudices passed down through the centuries as well as the origin of money lending and banking which undoubtedly cast Jews in a bad light.
This documentary had some good examples as well as an overall interesting view of money itself: http://en.wikipedia.org/wiki/The_Ascent_of_Money
Edit: And this is now getting downvoted why? What the hell is going on here?