you wrote:
“The irony here is that Ambrose would be spinning in his grave if a pope told him that he must accept the dogma of the IC.”
I’m not so sure of that.
Ambrose of Milan:
Come, then, and search out your sheep, not through your servants or hired men, but do it yourself. Lift me up bodily and in the flesh, which is fallen in Adam. Lift me up not from Sarah but from Mary, a Virgin not only undefiled but a Virgin whom grace had made inviolate, free of every stain of sin (Commentary on Psalm 118:22-30 [A.D. 387]).
Being free from the stain of sin is the condition of all the righteous.
“Purge me with hyssop, and I shall be clean; Wash me, and I shall be whiter than snow.” (Ps. 51:7)Mary is nothing special in this regard. Given what Ambrose said elsewhere it’s hard to take his comment about Mary as supporting the IC theory.
So, then, no one is without sin except God alone, for no one is without sin except God. (On the Holy Spirit)