Christianity, from its beginnings, while feeling bound to Judaism, developed an intense hostitlity and hatred of its mother faith. The writings of the Church Fathers, those who developed the Theology of the Church during the early centuries of Christian expansion consistently display a profound contempt for the religion of the People of Israel, an attitude that continues down to the present day. This hatred of Judaism was eventually formalized, legalized, and incorporated into all aspects of Christian legal and religious thought and expression.
There are several stages in the rise of Christianity to the point where it became the religion that dominated the Roman world. The first was the period when the earliest Christian communities were being persecuted for their faith by the Roman authorities. Christian martyrs were killed because of their adherence to faith in Christ. If we should ask why they were persecuted, in view of the fact that the Pagan emperors of Rome were tolerant of all religions and declared them legitimate, the answer liues in Christian behavior at that time.
In the earliest phases of the growth of the Church, Christians were not loyal citizens. They would not salute the imperial symbols, they did not consider the emperor to be a legitimate ruler. They believed only in the Kingdom of God in Heaven and would offer no recognition of mortal human kingship; they refused to recognize human authority.
We in America are tolerant beyond measure. In our country we have the freedom to refuse to salute the flag, we are not bound to declare the Pledge of Allegiance, and we are even protected by law if we choose to burn the flag as a statement of protest since it was defined by the Supreme Court as a form of speech whose freedom is protected by the Constitution. The Roman emperors would not countenace such liberal freedom. Any and all religions were recognized as legitimate in Rome. But it was expected that members of a defined religious community were loyal citizens of the state.
Since Judaism was a religio licita, a legal religion, Jews were free to practice their faith openly. In fact, the emperors even granted special exemptions to the Jews. In view of the law which prohibited mutilation, circumcision could be considered a crime. But the Jews were exempt in the case of circumcision because it was recognized as an essential part of the fundamental covenant between God and the Jewish People. Even the imperial standards, which always accompanied armed forces wherever they went, because they had sculptures of living beings on them would not be brought into the city of Jerusalem; the Jews objected to graven images in any form being brought into their Holy City. The Roman emperors agreed to exempt the Jews from this practice.
In many respects, the Pagan emperors of Rome were quite tolerant of all religions. But it was expected that all inhabitants of the empire; Persians, Egyptians, Greeks, and Jews would observe the norms of loyalty and patriotism. Only Christians would not agree. It is for this reason they were persecuted.They were seens as rebels, as subversives. Clearly they were not understood and they could not convince the authorities that they had the right to refuse to perform the symbolic acts of loyal citizens.