Paul calls unbelieving Jews mutilators if they force Gentiles to get circumcised (Philippians 3:2). They were engaged in an act of pure evil because it undermined the Gospel of grace. It twisted the doctrine of Gentile grafting (Romans 11:17-24) that made them equal participants in the family of God. This is interesting given that the procedure was the key identification of the covenant God made with the Jews. But that’s the point. It was simply a sign among the Jews that doesn’t apply to Christians now (Jew or Gentile). Circumcision is a choice, not a requirement. A Jewish flavored Christianity is not a special form of Christianity. Being a Jewish Christian is not better than being a Gentile Christian. In fact, these Jews were not real Christians at all. The controversy that drove Paul to call these heretics dogs (ancient profanity) was the teaching that Gentile, New Testament, New Covenant faith was somehow insufficient and in need of ritual Judaism. The New Testament doesn’t tell believers to have their sons circumcised. If the procedure is thought to contribute to salvation, it is nothing more than the idolatrous cutting and body markings condemned by the Old Testament (Leviticus 19:28). It mutilates the Gospel.