AOA, it looks like you just supported my point even more, so I'm not sure why you're keen on this distinction. My point was that your implication that the Qur'an "implicitly sanctions" circumcision (i.e. implies approval/authorization as per your own definition) is dangerous because such logic can be used to imply Qur'anic approval/authorization of things like slavery and subjugation of women.
Your three points are self defeating since you yourself have no "language" from within or outside of the Qur'an that supports them. You just assume that certain prevailing practices in the Muslim world, such as circumcision, formed the Millat of prophet Ibrahim due to their long history, with no evidence to support this argument, neither within the Qur'an, nor without. What could be more arbitrary than that? You say that I'm "discarding the language of the book with reference to the verses talking about the Millat of Ibrahim", yet are unable to point to any evidence inside or outside the Qur'an that circumcision is a part of this Millat. Whereas I based my argument entirely on the Qur'an itself:
69:40 This is the revealed Word in the dialect of a noble Messenger. [44:58]
69:41 This is not the utterance of a poet. Seldom do you choose to believe.
69:42 Nor is it the word of a soothsayer. Little of your intellect do you bring to use.
69:43 It is a Revelation from the Lord of the Worlds.
69:44 And if he had ascribed his sayings to Us,
69:45 We would have taken him by the right hand,
69:46 And would have cut off his Aorta. [‘Wateen’ = Artery of the heart = Life line =Life-artery = Strength]
69:47 And none of you could stop Us from doing that.
That said, there's nothing necessarily wrong with using such circumstantial evidence to support a good argument. But for me this argument is both poorly formed and dangerous.
As to your last point on slavery and subjugation of women not being the creed of Ibrahim, you're missing the point. Of course I don't think anyone on this forum at least thinks so, but millions of Muslims across the world would happily defend at least one of these by just such hadith-influenced interpretations of the Qu'ran. Even slavery and concubinage is not off the table when it comes to ISIS. And your argument would lend divine credence here since these practices were far more common during the times of prophet Ibrahim.