Quite a lot, if you would research. Rome was handed to the early church on a silver platter. It ought to have refused out of humility.
I tend to agree with you. When Christianity became the state religion, Christian people would pretend adherence in order to be thought better of by the Emperor. That just about always ends up corrupting people's intentions.
However, that sentence would be clarified a bit if it were noted that the church reformers (I am not talking about the Reformation, I am talking about e.g. the Hildebrandian/Gregorian, Cistercian reforms --- the many reforms before the 16th century )--- almost always had as their object, the reform of the clergy and freeing of the Church from the corruption of benefices and the control of princes.
The control of the State came back with a vengeance in the 16th century Wars of Religion, when the universal church was vivisected along national lines, became precisely identified with nationalism (Church of England, Church of Scotland, Church of Sweden, Church of a dozen German landgraves and princes.)
Again, you wrote: “Quite a lot... he does not understand biblical boundaries.”
And I’m asking. . . Such as? Tell me how he doesn’t understand “biblical boundaries.”