Thankfully, God did not stop the Reformation with Luther. He continued to reform the church then, as He does today.
[Luther] allows himself to be carried beyond all due bounds with his love of thunder...in the Church we must always be upon our guard, lest we pay too great a deference to men...If this specimen of overbearing tyranny has sprung forth already as the early blossom in the spring-tide of a reviving Church, what must we expect in a short time...Let us therefore bewail the calamity of the Church...
Calvins rage was unwise. In 1545 Luther was not only a dying man but one often immobile from excruciating bouts with kidney stones. Yet in 21st Century eyes even Johns self-important rage pales beside his intolerance of opposing views. For Calvin the persecuted became Calvin the persecutor. He particularly disliked a man named Servetus for his expressed views on Christian doctrines. In a letter to a friend John warned:
Servetus lately wrote to me and coupled with his letter a long volume of his delirious fancies...He would like to come here if it is agreeable to me. But I do not wish to pledge my word for his safety. For, if he comes, I will never let him depart alive, if I have any authority...
That grim warningI will never let him depart alivewas not just rhetoric. Foolishly, Servetus did show up in Geneva. And John Calvin did have some authority. Servetus was arrested and condemned to die. Genevans feared no interference because the Catholics in France had also given Servetus a death sentence. Just what was John Calvins part in the execution? Could he have prevented it? It seemed his mercy extended only to recommending beheading instead of burning. Genevans burned Servetus to death in 1553.
[Sources: T.H.L. Parker, John Calvin: a biography. Philadelphia: Westminster Press, 1975, and Jules Bonnet, editor, Letters of John Calvin. UK: Banner of Truth Trust, abbreviated English translation of 1855-57 edition in French, 1980.]