[monkfan]

At the risk of repeating things you doubtless know, the title of Theotokos (birthgiver of God) was confirmed by the 3rd Ecumenical Council. It is not a Mariological title, it is primarily a Christological doctrine. If Christ was fully God and fully man in one single person, not two (as Nestorius claimed), then Mary was and is the birthgiver of God.

Indeed! This was no small matter. Saint Nicholas (yeah, that St. Nicholas) actually went so far as to punch Nestorius for claiming that Mary was merely the Christotokos. These guys weren't kidding around.

[Agrarian]

I always heard it was Arius that St. Nicholas slapped, at the 1st Council.

Regardless, you are absolutely right that these guys were deadly serious -- they were not sitting around smoking cigars and agreeing with each other out of politeness.