1. 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. 
2. Calvin believed that the Eucharist provides an undoubted assurance of salvation.
Resembling the Roman Catholic view, Calvin stated that the sacrament of the Eucharist provided the “undoubted assurance of eternal life to our minds, but also secures the immortality of our flesh.” 
3. Calvin believed that the Reformed Church (his church) was the true Church and there was no salvation outside of it.
Calvin persuaded an Anabapist named Herman to leave the Anabaptists (which he considered a sect), and join the Reformed church. He wrote the following, which sounds strikingly similar to the way the Catholics of that time spoke of the Roman Catholic Church:
“Herman has, if I am not mistaken, in good faith returned to the fellowship of the Church. He has confessed that outside the Church there is no salvation, and that the true Church is with us. Therefore, it was defection when he belonged to a sect separated from it.” 
4. Calvin believed it was acceptable to lambast his opponents with vicious names.
Calvin treated his critics with contempt, calling them “pigs,” “asses,” “riffraff,” “dogs,” “idiots,” and “stinking beasts.” In this vein, Calvin said this of the great Anabaptist leader, Menno Simons: “Nothing could be prouder, nothing more impudent than this donkey.”
5. 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]
6. Calvin believed that Jewish people were impious, dishonest, lacked common sense, were greedy, and should die without pity.
Calvin wrote, “I have had much conversation with many Jews: I have never seen either a drop of piety or a grain of truth or ingenuousness – nay, I have never found common sense in any Jew.” 
Calvin is also quoted as calling Jews “profane dogs” who “under the pretext of prophecy, stupidly devour all the riches of the earth with their unrestrained cupidity.” 
He also stated that “their rotten and unbending stiffneckedness deserves that they be oppressed unendingly and without measure or end and that they die in their misery without the pity of anyone.” 
7. Calvin believed that God did not create all humans on equal terms, but created some individuals for eternal damnation.
This idea is known as “double predestination.” According to this view, God predestines some to salvation and others to destruction. While this idea will not be shocking to some Christians, particularly Calvinists, the idea that God would knowing create some individuals so as to destroy them eternally in the end is shocking to many believers.
According to Calvin, “The predestination by which God adopts some to the hope of life, and adjudges others to eternal death, no man who would be thought pious ventures simply to deny . . . By predestination we mean the eternal decree of God, by which he determined with himself whatever he wished to happen with regard to every man. All are not created on equal terms, but some are preordained to eternal life, others to eternal damnation; and, accordingly, as each has been created for one or other of these ends, we say that he has been predestinated to life or to death.” 
Chapter 21 of Book III of John Calvin’s Institutes of the Christian Religion is called “Of the eternal election, by which God has predestinated some to salvation, and others to destruction.”