I am discussing and debating the various subtle doctrinal differences between Roman Catholicism and Eastern Orthodoxy with a very close friend of mine. One question I've asked is, "How do Orthodox Christians view the Immaculate Conception."
His exact answer was:
Orthodoxy believes the Immaculate Conception to be superfluous. Saint Gregory the Theologian (4th c.) writes regarding the Incarnation, "That which has not been assumed has not be saved." To make the Virgin Mary free of the taint of original sin pulls her out of the human chain, robbing Jesus of the Father's will for him to assume all of our fallen humanity in order to redeem and save it. (2 Cor. 5:21; Gal. 3:13a)
I think this is a pretty solid argument.
Especially the part that says:
To make the Virgin Mary free of the taint of original sin pulls her out of the human chain, robbing Jesus of the Father's will for him to assume all of our fallen humanity in order to redeem and save it.
What explanation does the Catholic Church put forth to refute the statement above?
I think my question above differs from this question because I'm not necessarily asking for a scriptural argument (although it would definitely be welcomed).
To be clear, I am only interested in answers that are aimed at defending the doctrine of the Immaculate Conception.