In 1554, an eminent and famous Christian scholar—Sebastien Castellio—set this spark of liberty aloft in his book entitled Concerning Heretics.3 Castellio was a one time Calvinist and companion of Calvin for many years. In this book, he explained his shock and dismay at Calvin’s role in Servetus’ execution.
Specifically, Castellio charged Calvin with “murder.” Castellio explained: “I am no defender of Servetus, but I shall so expose the false doctrines of Calvin that every one shall see as plain as noonday that he thirsted for blood.”4
Rives, Stanford. Did Calvin Murder Servetus? (Kindle Locations 247-252). . Kindle Edition.