“Does a fountain send forth at the same place both sweet and bitter water?”
Did you know that John Calvin staunchly believed that executing unrepentant heretics was justified? Did you know that despite his reading of the New Testament he continued to believe that Old Testament capital offenses should be enforced today– such as rebellious children being executed? Did you know that when one individual in Geneva had the gall to call Calvin an “ambitious and haughty hypocrite” Calvin conceded to having him arrested, tortured, nailed to a stake and then beheaded for heresy? Did you know that during his influential, pastoral rule over Geneva there were 139 recorded executions? Did you know that one of John Calvin’s friends implored him to repent of his despotism and departure from Christ’s mercy, stating, “If Christ himself came to Geneva he would be crucified” (see article below).
Since Christ died for his enemies and commanded his followers to likewise love and pray for their enemies, there is no greater blasphemous heresy one can engage in than to kill one’s enemies in the name of Christ– no matter how heretical you think their teachings depart from your own. Sadly one’s views didn’t have to depart very far from John Calvin’s before he deemed you worthy of being banished or put to death– such as Anabaptists who propagated a belief in adult baptism over his view of infant baptism. 
In defending his role in having the Spaniard heretic, Michael Servetus, burned at the stake (though Calvin initially sought for him to be beheaded), Calvin made this shocking statement: “Many people have accused me of such ferocious cruelty that I would like to kill again the man I have destroyed.” 
To be sure we all have our sins and failures, and it is only fair that we view Calvin in light of the moral standards of his age, but we must never forget that for all Christians–no matter the age they live in– the New Testament is the standard by which all other standards must be measured. And as far as the timeless, unqualified teachings of Christ are concerned, to kill a heretic for being a heretic always makes you the bigger heretic. Or we might put it another way: to kill a perceived enemy of the gospel for being an enemy of the gospel always makes you the bigger enemy of the gospel. Here are two excerpts of a well researched article by Frank Viola:
Calvin believed that executing unrepentant heretics was justified.
The best known example of this is when Calvin consented to the execution of Michael Servetus, a man who denied the Trinity and infant baptism. Servetus burned for one hour simply because of his theological views. Calvin supporters are quick to point out that the great Reformer didn’t directly execute the man. He even tried to persuade Servetus not to come to Geneva. Calvin also tried to get Servetus to repent and sought for him to be granted a more humane execution (which was beheading instead of burning).
Even so, Calvin made this remark regarding Servetus, showing that he believed death for heresy was justifiable. “But I am unwilling to pledge my word for his safety, for if he shall come [to Geneva], I shall never permit him to depart alive, provided my authority be of any avail.” 
During Servertus’ trial, Calvin remarked: “I hope that the verdict will call for the death penalty.”  Nine years after the execution, Calvin made this comment in answering his critics: “Servetus suffered the penalty due his heresies, but was it by my will. Certainly his arrogance destroyed him not less than his impiety.” 
Calvin is also quoted as saying, “Whoever shall now contend that it is unjust to put heretics and blasphemers to death will knowingly and willingly incur their very guilt. This is not laid down on human authority; it is God who speaks and prescribes a perpetual rule for his Church.” [3a]
Whether you agree with Calvin’s view or defend his actions because he was “a man of his times,” many Christians find the idea of executing heretics to be shocking. This brings up another point for another post, but consider for a moment if murder was legal in our time. If it were, I think we’d have a lot of dead Christians who lost their lives to other Christians over doctrinal trespasses. If you think I’m wrong, just watch the vitriol and hatred in many “Christian” online forums as they verbally bludgeon one another over theological interpretations.
In addition to Servetus, Jerome Bolsec was arrested and imprisoned for challenging Calvin during a lecture, then banished from the city. Calvin wrote privately about the matter saying that he wished Bolsec were “rotting in a ditch.” 
Jacques Gruet was also a man who disagreed with Calvin. He called Calvin an ambitious and haughty hypocrite. The administrations of Geneva tortured Gruet twice daily until he confessed, and with Calvin’s concurrence, Gruet was tied to a stake, his feet were nailed to it, and his head was cut off for blasphemy and rebellion.
Pierre Ameaux was charged with slandering Calvin at a private gathering. He was to pay a fine, but Calvin wasn’t satisfied with the penalty, so Ameaux spent two months in prison, lost his job, and was paraded through town kneeling to confess his libel, also paying for the trial expense. 
Calvin believed that the Old Testament capital offenses should be enforced today.
The city of Geneva was ruled by the clergy, which was composed of five pastors and twelve lay elders chosen by Geneva’s Council. But Calvin’s voice was the most influential in the city. Here are some laws and facts about Geneva under Calvin’s authority:
* Each household had to attend Sunday morning services. If there was preaching on weekdays, all had to attend also. (There were only a few exceptions, and Calvin preached three to four times a week.)
* If a person came to the service after the sermon had begun, he was warned. If he continued, he would have to pay a fine.
* Heresy was regarded as an insult to God and treason to the state and was punished by death.
* Witchcraft was a capital crime. In one year, 14 alleged witches were sent to the stake on the charge that they persuaded satan to afflict Geneva with the plague.
* Clergy were to abstain from hunting, gambling, feasting, commerce, secular amusements, and had to accept annual visitations and moral scrutiny by church superiors.
* Gambling, card-playing, frequenting taverns, dancing, indecent or irreligious songs, immodesty in dress were all prohibited.
* The allowable color and quantity of clothing and the number of dishes permissible at a meal were specified by law.
* A woman was jailed for arranging her hair to an “immoral height.”
* Children were to be named after Old Testament characters. A rebellious father served four days in prison for insisting on naming his son Claude instead of Abraham.
* To speak disrespectfully of Calvin or the clergy was a crime. A first violation was punished by a reprimand. Further violations with fines. Persistent violations were met with imprisonment or banishment.
* Fornication was punished by exile or drowning.
* Adultery, blasphemy, and idolatry was punished with death.
* In the year 1558-1559, there were 414 prosecutions for moral offenses.
* As everywhere in the 16th century, torture was often used to obtain confessions or evidence.
* Between 1542-1564, there were 76 banishments. The total population of Geneva then was 20,000.
* Calvin’s own step-daughter and son-in-law were among those condemned for adultery and executed.
* In Geneva, there was little distinction between religion and morality. The existing records of the Council for this period reveal a high percentage of illegitimate children, abandoned infants, forced marriages, and sentences of death. 
* In one case, a child was beheaded for striking his parents.  (Following Old Testament Mosaic law, Calvin believed it was scriptural to execute rebellious children and those who commit adultery.) [10a]
* During a period of 17 years when Calvin was leading Geneva, there were 139 recorded executions in the city. 
Sabastian Castellio, a friend of Calvin’s who urged him to repent of his intolerance, made the shocking remark, “If Christ himself came to Geneva, he would be crucified. For Geneva is not a place of Christian liberty. It is ruled by a new pope [John Calvin], but one who burns men alive while the pope at Rome strangles them first.” 
Castellio also made this remark: “Can we imagine Christ ordering a man to be burned alive for advocating adult baptism? The Mosaic laws calling for the death of a heretic were superceded by the law of Christ, which is one of mercy not of despotism and terror.” [12a]
Click HERE to read the entire article (with source citation), including more shocking beliefs of John Calvin, such as his view that Jews were “profane dogs” and should “die in their misery without pity of anyone.”
 See Defense of Orthodox Faith against the Prodigious Errors of the Spaniard Michael Servetus, published in 1554
 A visiting Anabaptist by the name of Belot was arrested for passing out anabaptist literature in Geneva. His books and tracts were confiscated and burned and Belot was banished from the city. He was warned that if he returned he would summarily be arrested and hanged. (See J.L. Adams, The Radical Reformation, Westminster Press, 1967, p. 597-598)