Yes I realize this is the RCC position that arose in the defense of Nestorian heresy, i.e., that Jesus was 2 separate individuals (human and divine) rather than the unique only begotten God-man both human + Divine. So the attempt was to call Mary the 'Mother' of God so as not to separate the divinity from the humanity of Christ which was felt could lead to further heresy.
But how the RCC has gone into the other ditch and has devolved itself into Marian heresies. By calling Mary the "Mother of God" she (Mary) has now been raised into divinity status herself, without sin, now she is prayed to, bowed to, exalted, and made a co-redemptrix equal with Christ or even greater in some cases. All blasphemous heresies.
Mary is the Mother of the humanity of Christ. She is not and never has been the source of His divinity. Nor was she ever conceived without sin. This can be seen from her statements in Luke 1:47-48...God my Savior in v. 47 and humble estate in v. 48. (KJV uses the translation low estate). The Greek text is ταπείνωσις (tapeinōsis) which means:
"ταπείνωσις (tapeinōsis, 5014), -εως, ἡ, (ταπεινόω), lowness, low estate, [humiliation]: Lk. i. 48; Acts viii. 33 (fr. Is. liii. 8); Phil. iii. 21 (on which see σῶμα, 1 b.); metaph. spiritual abasement, leading one to perceive and lament his (moral) littleness and guilt,"
A humble sinner isn't going to be the source or 'Mother' of God. God has existed from all eternity, Christ is the one who in His pre-incarnate state is the Creator, the Creator (Christ) created Mary, as the Creator God He has no need of a 'divine' Mother. But to be the Redeemer of man He needed to become human to take the sins of man upon Himself and provide for our salvation. It is his humanity that Mary is the Mother of - not the divine.
Here's what Christ actually said about it: "For whoever does the will of My Father who is in heaven, he is My brother and sister and mother." Matthew 12:50. (Cf. John 19:26-27). Christ took the focus OFF Mary and so should we. I'm willing to bet that Christ knew a future time would come when Mary would be exalted and He headed those heresies off at the pass with these veres.
"At that time, therefore, when about to engage in divine acts, He repelled, as one unknown, her who was the mother, not of His divinity, but of His [human] infirmity." (St. Augustine: NPNF1: Vol. VII, Tractates on John, Tractate CXIX, §1, John 19:24-30)
But we hold the human nature of Christ is united to the Divine nature in one person.
She is not and never has been the source of His divinity.
Agreed, except in so far as his Divinity is inseparable from his humanity.
Jesus, as Paul tells us in the second chapter of Philippians, was as humbled as ever anyone could be humbled. The link between humility and quilt is certainly usually the case. But it is not logically necessary. One can be guilty without being humble and humble without being guilty.
What you said.
Correct, plus it is a true statement. The further heresy is evident today as well by the same cause.
But how the RCC has gone into the other ditch and has devolved itself into Marian heresies. By calling Mary the "Mother of God" she (Mary) has now been raised into divinity
No, Mary is not God according to Catholic teaching. Mary is the mother of God, or theotokos, according to Catholic teaching. Variance from either is in error according to Catholic teaching.
As a corollary there are Nestorian and Arian type heretics among protestants, but this is not in accordance with any mainstream Protestant theology. A lacking in knowledge of who Mary is can result in an erroneous knowledge of Christ. It works both ways.
The answer is not to teach falsely about Mary or Jesus, not to avoid teaching the truth of Mary as the mother of God.