The reformation was not a garden tea party. It killed 30% of the population of central Europe. Every leader involved, including the so-called "reformers", can be found in print urging that his opponents be exterminated in the name of God.
There was a peasant revolt against the Church of Rome (as the peasants felt the Church was part of the establishment keeping them in poverty) and there was a political revolt by people in power in countries outside Italy against domination of their governments and monarchies by the Church of Rome.
These are the underpinnings of the "Reformation." There probably wouldn't have been a Reformation if the Roman Catholic church at that time hadn't wanted political domination and not wanted to repress dissenting views. It is in many ways similar to the problems Islam is having today.
Yes, there was a slaughter. I believe Martin Luther condemned taking arms against established authority, and thus ruling authorities in Germany felt free to put down their peasant revolt. And for this reason his reformation was rejected in those parts of Germany-Austria where the slaughter occurred.
If you have writings of Martin Luther urging physical extermination (death) for his opponents, I'd be interested in a citation. There was a supposed proponent of Luther's who was very blood thirsty, but he was renounced by Luther, IIRC.