Way before Martin Luther and Protestantism the Catholic Church were burning people, heretics, because of a book they didn't take literally ???
My god what type of people were they.
All of that was less about textual literalism, and more about public adherence to doctrine about theology, philosophy, and practice.
Though it's a stretch to say it was "way before" Luther. It wasn't
that long before his time that the Catholic Inquisitions were established. It's mostly a phenomenon of the High and Late Middle Ages.
The Church largely lacked the centralized power to enforce itself between the collapse of the Western Roman Empire in 476 CE and the resolution of the Investiture Controversy in the 1100s CE, so it often relied on secular authorities to do that for them-- which of course was made complicated by the political motives of those princes. The Church wasn't an entirely politically unified entity either, even in the West, and bishops had a lot of local power too, which made that enforcement very complicated and not really centralized.
The Mediaeval Inquisition, the first real attempt at a Church-driven, centralized process to stamp out heresy, only really emerged in the 1200s. It was organized, not by the Pope, but by individual bishops, and mostly in reaction to the Cathar movement-- which was a highly organized, popular heretical group-- not really as a response to the occasional peasant that questioned the Bible or didn't go to Mass or had beliefs that deviated from the norm. And
that wasn't entirely cut and dry either, as the Pope initially didn't want violence against heretics, and excommunicated bishops that approved of lynching, instead hoping that just better explaining Church teaching would be sufficient. When it really got underway and was radicalized into severely persecuting heretics, it mostly followed on the heels of successful
secular military intervention against Cathars and Waldensians. It was never just about the Church and religious doctrine, but I'd say it was mostly about secular power which the Cathars (who rejected the swearing of oaths) threatened. The Inquisition, at least in the Middle Ages, was more of a legal inquiry that exposed heretics; all of the killing, maiming, and exiling was done by secular authorities, as public heresy was usually a civil crime relating to disturbing the peace-- it's just, in those times, punishment for public disobedience was death.
And by the 1400s, the power relations had gone back around, and control over ecclesiastical affairs slipped out of the hands of the Pope in Rome, which would continue in the 1500s. The Inquisition in the Early Modern Period became more of a tool of kings and proto-nations. The Spanish Inquisition, for instance, was approved of by the Pope but was established and wielded by the Spanish monarchy as a tool to build a Christian Spanish nation and ethnically cleanse Jews and Muslims from Spain. The Inquisition's condemnation of Joan of Arc in 1429 was
entirely political, to the point that her conviction was overturned 30 years after her death once the French Kings won the Hundred Years War.
So by the time we get to Martin Luther in 1519, the Inquisition had been kicking around for only about 300 years, and half of that was spent under the direction of local or national leaders, rather than under the centralized Church. It was a fairly recent institution, with a considerable amount of corruption and secular politicking attached to it.
