CANON IIf anyone will not confess that the Emmanuel is very God, and that therefore the Holy Virgin is the Mother of God ([theotokos]), inasmuch as in the flesh she bore the Word of God made flesh [as it is written, "The Word was made flesh"] let him be anathema.
Deo gratias, Brother in Christ! Pax vobiscum!
F
Calling Mary the "mother of God" is a wholly different thing than calling her the MOTHER of God. Inasmuch as she bore the body of the incarnation and is the fleshly mother of Jesus I believe there is no disagreement in regard to her title as the mother of Emmanuel, God with us -- and in that sense (and that sense alone - she is properly referred to as the mother of God.
The problem is that when many Catholic's refer to Mary as the Mother of God, they appear to attach some spiritual significance such that Jesus (as the son of Mary) becomes subject to the will of Mary rather than Mary being subject to the will of her Lord, Jesus.
A Certain unmentionable sect in Utah believes that Jesus had a heavenly Mother and they used to teach (they now deny that they ever taught it) that Jesus was begotten in the Flesh by God the Father and thus Mary is the literal Wife of the Father (both Spiritually and physically) and the Mother of Jesus. So when we get into this "Mother of God" stuff one clearly has to tiptoe through the Heresies so that it is clear that God does not exist simply because he was the physical child of Mary.
I have actually seen posts here that suggest that if Mary had not been faithful, if it were not for Mary's part in the redemption, that Jesus would have been powerless to save the world. That is the kind of Marian Worship heresy that will keep protestants away from full communion with Rome for a long time.