Why did Calvin reject these Catholic doctrines about Mary?

The Catholic Church has a few teachings about the Mother of our Lord that are not accepted by many Protestants. This is not evident in the doctrines of many early Protestant reformers including Luther, Zwigli, and Bucer. From a theological standpoint, many protestant viewpoints do not differ significantly from the Roman Catholic doctrines concerning Mary. Calvin, on the other hand, does. For instance, Calvin disagreed with the practice of calling Mary the "mother of God," saying, >"I cannot think such language either right, or becoming, or suitable. ... To call the Virgin Mary the mother of God can only serve to confirm the ignorant in their superstitions. Consider for example, - The Immaculate Conception of Mary - The Assumption of Mary - The perpetual virginity of Mary - The intercessory role of Mary It's been said that Calvin's genius was not in creating new ideas but in developing existing thought to its logical conclusion. Did Calvin comment on these doctrines? What were his conclusions?