I'll tell you why ... because Roman Catholics are grotesquely negligent in pointing out that there is nothing divine about Mary. Mary was/is a human being, she is currently a disembodied spirit awaiting her resurrection body like the rest of the OT and NT believers. Jesus did not receive his divine nature from Mary ... and the term Mother of God implies that He did ... and the importance and position that they ascribe to her thoroughly clouds the topic.
Maybe you should give enough credit to those fifth-Century bishops to understand that they had no intention of implying that Jesus got his divine nature from a mortal woman, something that even the dumbest, last-in-his-class undergraduate theology student understands is impossible, for the simple reason that nobody can give what he doesn't have.
because Roman Catholics are grotesquely negligent in pointing out that there is nothing divine about Mary.
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You should be ashamed to be posting such obvious nonsense!