If I believe that Circumcision in the flesh is no longer required for Christians today in the New Covenant, how is that being in rebellion towards God?
Because your belief contradicts what God himself said. Did you see the image I posted of the gay pastor? Based on what you just stated he could just as easily ask " If I believe that homosexuality is no longer sin for Christians today in the New Covenant, how is that being in rebellion towards God?" and you couldn't say a single thing to him because it's his belief versus your belief. It's his interpretation of the Bible versus your interpretation of the Bible.
Spiritual circumcision aka circumcision of the heart is not a new testament/new Covenant thing. Someone told me that in the old testament circumcision of the heart is mentioned more than circumcision of the flesh. I haven't sat down and counted the mentions of both but I have no reason to doubt the validity of that statement. For one circed at birth they still need to have a circed heart. For one not circed at birth they will have the circed heart first at Salvation but out of obedience to and love for God the circ of the flesh should follow.
Knowing God is a just God and that the Bible cannot contradict itself and that there were men who taught that circ of the flesh would earn you salvation I would say that any time it seems someone is speaking against circ they are speaking against it as a means for salvation.
RE: Contending for the Faith: part 1 of ?