Actually, I'm more of an agnostic than anything else and a big part of the reason is that I see the spread of Christianity directly related to the force of arms.
If Western Europe became Christian, it was in large part due to the Imperial mandate of the Roman Empire and then the Christianized barbarians. At the time of the Christian (Arianism-variety) Visigothic invasion of Roman Spain, most of the rural population of Hispania was still pagan.
When the supposed Protestant "Reformation" came about, it was begun and carried out by men that would be considered homicidal fanatics by today's standards.
This should be your first hint. Go back and study how Catholicism coalesced in the time of Constantine. At the same time, study what happened to the religions of rome as they were swallowed up by catholicism one by one.
Rome was known through it's history not only of being tolerant to all religions; but, of compelling public commitment to the gods recognized by the empire. To be a roman was to belong to a Universal religion that believed in and respected all the gods.. little g. Now out of that through forced conversion you get the Universal Church as it swallows up at sword point all the other religions, renaming their pagan rights and customs and adding to the scriptures till the end product is Christianized pagans. Not Christian pagans; but Christianized.. having a form that looked like Christianity on the ever so delicate facade. It has a different definition of sin, A works based salvation stored up in a treasury from which Rome dispenses Salvation in little doses at a time and calls it "grace". On and on we go. The terminology is the same until you define your terminology, then the differences pile up like holstien carcases at a hoof 'n mouth sioure'.
What Rome was doing with the inquisitions was not Christian and in no way condoned or taught in Christianity any more than what the Protestants did in the witch trials. What you see is the product of religious groups practicing philosophy - NOT Christianity. If they'd been practicing Christianity instead, we wouldn't be having this discussion.