Is it true that Christians burned people at the stake, like those who were thought to be witches?
Mediums and Witches
The Bible does mention witchcraft and it often associated with divination, mediums, and spiritists, and where the Bible does speak about it, it is not good. The word used for “witchcraft” is the Hebrew word “anan” and means “to make appear, produce, to conjure,” or “to perform soothsaying.” The NASB translates Moses writing, “There shall not be found among you anyone who makes his son or his daughter pass through the fire, one who uses divination, one who practices witchcraft (“anan”), or one who interprets omens, or a sorcerer” (Deut 18:1), but Israel refused to Listen. As a result of disobeying this command, some of Israel’s kings became so wicked that they actually participated in divination or witchcraft. One such example was King Manasseh, who “made his sons pass through the fire in the valley of Ben-hinnom; and he practiced witchcraft, used divination, practiced sorcery and dealt with mediums and spiritists. He did much evil in the sight of the Lord, provoking Him to anger” (2nd Chron 33:6). Imagine something so evil that they actually sacrifice their own children in the fire! Since witchcraft is not from God, then it must be of Satan and his demons. Jesus said whoever is not with Him is against Him (Mark 9:38-41), so anyone who says that there are “good witches” doesn’t even understand that no human is “good” in God’s sight (Rom 3:10-12), and God sees the practice of witchcraft as an abomination  to Him and those who practice sorcery and witchcraft will end up in the lake of fire (Rev 21:8). This is infinitely beyond being a “gray area.”
Salem Witch Trials
In the 17th century, there were a series of hearings over people suspected of witchcraft. These hearings first began in Colonial Massachusetts in February 1692 and lasted until May 1693. Even though these were referred to as the Salem Witch Trials, this label is incorrect because these trials were not only held in Salem, but in Salem Village (Danver), Salem Town, Ipswich, and Andover, but what is often forgotten about these trials is where all of this started. Suspicions about witches did not start in Salem or in their surrounding villages, but this was actually incited by one man and by rumors about witches. It appears to have all started with Cotton Mather who was the minister of Boston’s North Church. In 1689 he wrote a book called, “Memorable Providences Relating to Witchcrafts and Possessions,” and in it Mather writes about a boy who stole some linen from the washroom, but says the only reason he did this was because of a spell that the washwoman’s husband had cast on him, so basically, John Goodwin, the boy’s father, accused the washwoman’s husband of being a witch. Then Mather claims that most of Goodwin’s other children fell under a spell and they couldn’t even control their own body movements. This book created an atmosphere of fear in Colonial New England, but especially, in Salem, and it would result in a witch hunt.
The accounts recorded in Mather’s book sent many into a panic and on a “witch hunt” in their own villages and neighborhoods. Many of them began to look at each other with suspicion. Reverend Mather and his own undocumented imagination may have been behind the dozens of witch trials that would eventually sweep through Colonial New England and create such a witch-panic that dozens were hanged without having any conclusive, substantial, or even extenuating circumstantial evidence. Mather’s book is believed by many historians to be the primary reason for these witch trials, although much of this superstition came from England, where many of them had migrated from, so from the late 17th century until the early part of the 18th century, just about anything bad that happened in a village or neighborhood would cause people to fear and make people suspicious of others. This fear would often provide impetus for a witch hunt. Almost any misbehavior by children or natural catastrophes or even accidents was seen as evidence that someone or some persons might possibly be a witch. Even natural illnesses that people might get were seen as possibly being caused by a witch. Superstition  had overtaken reason.
There is no record of anyone ever being burned at the stake for being a witch in Colonial New England. Any movies or books that include this as happening are not indicative of what historically took place in Colonial America, however, there were Medieval laws of the Holy Roman Empire that ordered witches be burned by fire, and estimates are that there were over 50,000 people burned alive for being involved in witchcraft. Thankfully, this witch-hunt hysteria finally died out by the 18th century. In Colonial America, those found “guilty” of witchcraft were usually hanged, however a person thought to be a witch and who was subsequently convicted as such were far better off than those in Europe who were burned at the stake while the whole village watched. Most of the twenty or so victims were women, and all but one was hanged.
Fear is a dangerous thing, and religion that seeks to hurt or kill another over something or someone they fear and are suspicion about, is wrong, but tragically Christians were killing others without the right to do so but thought they were doing God a service. What they thought they were doing by hanging “witches” was good, but the road to destruction is paved with good intentions, and so good intentions are not enough. We need to trust God in this life to right every wrong and to straighten everything crooked. Yes, we should be change agents as much as possible in this world because we’re called to be salt and light, however, when we have done all we can, not breaking the law (Rom 13:1-5), we must let God judge their heart because only He can see it (1st Sam 16:7), and “Repay no one evil for evil, but give thought to do what is honorable in the sight of all. If possible, so far as it depends on you, live peaceably with all. Beloved, never avenge yourselves, but leave it to the wrath of God, for it is written, ‘Vengeance is mine, I will repay, says the Lord’” (Rom 12:17-19).
Take a look at this related article: What is a Pagan? 
Resource – Scripture quotations are from The Holy Bible, English Standard Version® (ESV®), Crossway Bibles. (2007). ESV: Study Bible : English standard version. Wheaton, Ill: Crossway Bibles. Used by permission. All rights reserved.