First because by calling me a Nestorian, I was being accused of heresy.
Second, because calling me a Nestorian was a clear misrepresentation of my stated belief.
Heresy only has a meaning within the Church. Since you are not in the Catholic and Apostolic Church, heresy should mean nothing to you.
A heretic is someone who professes a doctrine other that the doctrine of the Catholic and Apostolic Church. That is actually a "legal" definition of heresy – doctrine outside of, unrecognized as canonical by the Church.
For that matter, calling someone "Calvinist" would be just as "wrong" since, as far as the Catholic and Orthodox Churches go, John Calvin's teaching is outside the teaching of the Church.
Second, because calling me a Nestorian was a clear misrepresentation of my stated belief
If we misunderstood your beliefs, I apologize on behalf of all Catholics and Orthodox. Perhaps what you said misled us to believe you were subscribing to Nestorian beliefs.
I had been warning you that you were skating very close to adopting Nestorius's position back when you were advocating 'Mother of Christ' instead of 'Mother of God'. That's part of why I was insisting you find and read the acta of the Third Ecumenical Council. The others noticed, too. (I like to joke that we Orthodox are issued an 'I Spy Book of Heresies' at chrismation, so we can recognize them easily even in modern guises.)
While you're at it, the acta of the Fifth,would be good to read, too, since that council formalized as a doctrine the long tradition that Mary remained a virgin, 'before, during and after' giving birth to Our Lord, God and Saviour Jesus Christ, as well as condemning Theodore of Mopsuestia (Nestorius' mentor), and certain writings of Theodoret against Cyril of Alexandria and a letter of Ibas of Edessa to Maris (though not condemning Theodoret or Ibas themselves for heresy.