“Is He the God of the Jews only? And not also of the Gentiles? Yes, and of the Gentiles also. Since there is one God Who shall justify the circumcision by faith, and the uncircumcision through faith, ….”
When the Jews acknowledged that the Gentiles had other ‘gods’, it became a tacit admission recognizing those idols as something substantive, something to be considered. What any person believes about God and idols has no effect on the truth that God is, and idols are nothing: superstitions, fairytales, or demonic lies. YHWH, the Lord God Almighty, is the Creator of the universe, and the absolute sovereign over all men, regardless of whether they recognize Him, believe Him, or obey Him.
There is one God; He therefore must be the God both of the Jews and the non-Jews. All men everywhere are creations of and subjects to the only Living and True God. The identity of the Jews was in the forms and bloodline of their forefathers, but as God established His purpose from the beginning of time to redeem a people to Himself, He established one means by which all men would be justified before Him.