It goes back to Biblical times, when pharisee Jews persuaded the authorities to kill Jesus. Christians are HIS legacy.

Jerusalem was divided into quarters during the middle ages: Jewish, Christian, Muslim and Armenian (orthodox Christian, and a lot of the fighters came from that area - hence a geographic link rather than a religion) - and that was because all those people were there and needed some peace. So really, the anti-Christian hatred goes against a tradition that we fought for, a thousand years after Christ died. We all have links to Jerusalem. It is not a Jewish city. End of.