One which begged the question that the tradition originated with the Apostles, which you have yet to establish, and have only merely asserted.
The Church has always taken that verse literally, and not (as RD "merely asserted") as a metaphor. Prima facie, to modern, post-Reformation nondenominational Evangelical Christians, it appears that it at least possibly could be a metaphor, but the ancient Church never took the Scriptures according to their prima facie readings of them, but they always took Apostolic teachings as the prima facie meaning of Scriptures, and the Apostolic teachings on the "cloud of witnesses" is that it is literal.
In contrast to the Apostolic teaching on the verse, RD's view is: "can only be a metaphor. There is NO literal way to take that."
To use your phrase, RD's take is a mere assertion.
Genesis 17:9-14; Leviticus 12:3; John 7:22-23;
22 For this reason Moses has given you circumcision—not that it is from Moses, but it is from the forefathers—and you circumcise a man on a sabbath. 23 If a man receives circumcision on a sabbath so that the Law of Moses may not be broken, are you violently angry at me because I made a man completely well on a sabbath?
This is not an Apostle teaching circumcision, but is Jesus criticizing the Jewish teachers of the Old Covenant law.
19 Go, therefore, and make disciples of people of all the nations, baptizing them in the name of the Father and of the Son and of the holy spirit, 20 teaching them to observe all the things I have commanded you. And look! I am with you all the days until the conclusion of the system of things.”
This is not an Apostle teaching circumcision.
8 “He also gave him a covenant of circumcision, and he became the father of Isaac and circumcised him on the eighth day, and Isaac became the father of Jacob, and Jacob of the 12 family heads.
Stephen is not an Apostle, and Stephen wasn't teaching circumcision either, he was reviewing the history of the Old Covenant /Old Testament.
45 And the circumcised believers who had come with Peter were amazed, because the free gift of the holy spirit was being poured out also on people of the nations.
This is not an Apostle teaching circumcision.
2 So when Peter came up to Jerusalem, the supporters of circumcision began to criticize him,
Why would they criticize Peter if Peter, an Apostle, was teaching circumcision?
Now some men came down from Ju·deʹa and began to teach the brothers: “Unless you get circumcised according to the custom of Moses, you cannot be saved.”
Those "some men" are not said to be Apostles.
25 Circumcision is, in fact, of benefit only if you practice law; but if you are a transgressor of law, your circumcision has become uncircumcision.
Not an Apostle teaching circumcision.
Galatians 2:4, 7, 9, 12 (cf Acts 15:1).
4 But that matter came up because of the false brothers brought in quietly, who slipped in to spy on the freedom we enjoy in union with Christ Jesus, so that they might completely enslave us; ... 7 On the contrary, when they saw that I had been entrusted with the good news for those who are uncircumcised, just as Peter had been for those who are circumcised— ... 9 and when they recognized the undeserved kindness that was given me, James and Ceʹphas and John, the ones who seemed to be pillars, gave Barʹna·bas and men the right hand of fellowship, so that we should go to the nations but they to those who are circumcised. ... 12 For before certain men from James arrived, he used to eat with people of the nations; but when they arrived, he stopped doing this and separated himself, fearing those of the circumcised class.
I admit this is the closest you come to substantiating your claim that, “ The Apostles taught that you must be circumcized on the 8th day after birth. ” But it still falls short of proof. Nowhere does it say what any Apostles taught, it says there were men who did teach circumcision, but not that they were Apostles, and it says that Peter was conflicted, which is granted.
Because Paul had convinced them. (cf Galatians 2)
I feel that here, you are merely agreeing with me. Once the Acts 15 council was convened, there just wasn't even any doubt that no Apostles, or even any other teachers /bishops /elders, taught or would ever teach again circumcision (if they did, it would have been against the council's conclusion). btw it wasn't just Paul but also Peter who convinced them (Acts 15:7-11) that circumcision was not a part of the New Covenant.
Well, let me know what you think now.