If you want to pin the blame for what became anti-Semitism on someone, I think the Roman Empire is the most culpable candidate.
Think politically. By the time of Constantine's "conversion" in 313, Christianity was growing like wildfire in the Mediterranean, the Roman Empire was in decline, and the Romans were in the awkward position of being persecutors of this new religion. What better way to cut your losses and consolidate your eroding gains in the Middle East than to embrace the new upcoming movement (Christianity), while demonizing the old established order (Judaism).
So the early Christian church essentially made a pact with the devil; the Romans would cease persecution of Christians and assure their rise to dominance in the region, but the Christians must accept and include in their core scriptures polemics against the Jews (Constantine having considerable influence on what finally became, shortly after, the Christian canon); this, in spite of the fact that Jesus himself was a Jew, the vast majority of early Christians were Jews, and the Romans were directly responsible for the execution of Jesus.
Think politically. By the time of Constantine's "conversion" in 313, Christianity was growing like wildfire in the Mediterranean, the Roman Empire was in decline, and the Romans were in the awkward position of being persecutors of this new religion. What better way to cut your losses and consolidate your eroding gains in the Middle East than to embrace the new upcoming movement (Christianity), while demonizing the old established order (Judaism).
So the early Christian church essentially made a pact with the devil; the Romans would cease persecution of Christians and assure their rise to dominance in the region, but the Christians must accept and include in their core scriptures polemics against the Jews (Constantine having considerable influence on what finally became, shortly after, the Christian canon); this, in spite of the fact that Jesus himself was a Jew, the vast majority of early Christians were Jews, and the Romans were directly responsible for the execution of Jesus.