Scripture for the most part says that only those who believe in Jesus will receive salvation. Having a seminary professor suggest otherwise was a new experience for me. This is not to say that a Jew can not become a Christian or shouldn't become a Christian only that they need not become a Christian in order to be among God's people. They are already people of the covenant. They are inheritors of the promises to Abraham by birth.
Circumcision is a sign of the covenant, but the covenant is passed on by blood.
Which brings me to a new insight from the dialogue with Temple Beth El and Rabbi Stanway. I was not able to see it before, but most of Christian Scripture is a polemic against the Jews. The struggle of the fledgling church to find its place within Jewish history and faith led to many disputes with religious leaders and pious people. Those issues were so dominant during the first century of Christianity that they are reflected throughout the New Testament and had a big impact on what was written by the authors. The disputes lead to tension between Jews and Christians as the church found its place within society.