Anabaptists required that baptismal candidates be able to make their own confessions of faith and so rejected baptism to infants. As a result of re-baptism, Anabaptists were heavily persecuted during the 16th century and into the 17th by both Protestants and Roman catholics.  The Anabaptists insisted upon the “free course” of the Holy Spirit in worship, yet still maintained it all must be judged according to the Scriptures. The Swiss Anabaptist document titled “Answer of Some Who Are Called (Ana-)Baptists – Why They Do Not Attend the Churches” shows one reason given for not attending the state churches was that these institutions forbade the congregation to exercise spiritual gifts according to “the Christian order as taught in the gospel or the Word of God in 1 Corinthians 14.”  Common Anabaptist beliefs and practices of the 16th century continue to influence modern Christianity:

• Bible as the sole rule of faith and practice – the authority of the Scriptures
• Freedom of religion – liberty of conscience
• Separation of church and state
• Pacifism or nonresistance
• Separation or nonconformity to the world
• Voluntary church membership and believer’s baptism
• Evangelistic zeal
• Priesthood of all believers 

Persecutions by Protestants. 343 och A Short History of the Inquisition. 344, 346

Article IX: Of Baptism. Of Baptism they teach that it is necessary to salvation, and that through Baptism is offered the grace of God, and that children are to be baptized who, being offered to God through Baptism are received into God’s grace. They condemn the Anabaptists, who reject the baptism of children.

August 7th, 1536, a synod was convened at Hamburg to devise the best means of exterminating the Anabaptists. Not one voice among all the delegates was raised in favor of the Anabaptists. Even Melancthon voted to put all those to death who should remain, obstinate in their errors. The ministers of Ulm demanded that heresy should be extinguished by fire and sword. Those of Augsburg said: “If we have not yet sent any Anabaptists to the gibbet, we have at least branded their cheeks with red iron!? 

The Reformed church also fiercely persecuted the Anabaptists. The Anabaptists rejected infant baptism, and advocated immersion as the only effective form of holy bathing. Shortly before the convening of the diet of Augsburg, in 1534, Rothmann, one of the leaders of the Anabaptists, had openly preached in the streets of that city. He had won the people, who cried out to his opponents, “Answer Rothmann, Catholics, Lutherans, Zwinglians!”Luther and his friends answered Rothmann in the old persecuting way. The Anabaptists were excluded from the diet, and Luther wrote to Melanchthon that they were “ravenous wolves,” who harried the sheep-fold of Christ and “should be banished.” At the same diet the consistent Luther demanded liberty of conscience, churches in which to worship, and the full rights of citizenship. He was the prototype of our Sabbatarians, who demand “religious liberty,” while asking that laws be enacted to deprive everybody but themselves of liberty on Sunday. August 7, 1536, a synod was convened at Hamburg to take measures for the suppression of the Anabaptists.

Delegates came from all the cities which had renounced Catholicism. Not one spoke for the Anabaptists. Even the “gentle Melanchthon” voted for death for all who should prove obstinate in their errors, or who should return from banishment. “The ministers of Ulm demanded that heresy should be extinguished by fire and sword. Those of Augsburg said: If we have not yet sent any Anabaptists to the gibbet, we have at least branded their cheeks with red iron. Those of Tubingen cried out: Mercy for the poor Anabaptists who are seduced by their leaders, death to the ministers of this sect. The chancellor showed himself much more tolerant. He wished that the Anabaptists should be imprisoned, where, by dint of hard usage, they might be converted” (Catrou, ut supra, liv. i., 224; Zudin, 464).

This decree was issued: “Whoever rejects infant baptism; whoever transgresses the orders of the magistrates; whoever preaches against taxes; whoever teaches the community of goods ; whoever usurps the priesthood; whoever holds unlawful assemblies; whosoever sins against faith, shall be punished with death. As for the simple people, who have not preached or administered baptism, but who were secduced to permit themselves to frequent the assemblies cf the heretics, if they do not wish to renounce Anabaptism, they shall be scourged, punished with perpetuc.1 exile, and even with death if they return three times to the place whence they have been expelled“ (see Catrou, Gastius, Menzel and Meshovius).

That same year Luther wrote to Philip, Landgrave of Hesse: “Whoever denies the doctrines of our faith aye, even one article which rests on the scripture, on the authority of the universal teaching of the church must be treated not only as a heretic, but also as a blasphemer of the holy name of God. It is not necessary to lose time in disputes with such people; they are to be condemned as impious blasphemers.”

In the same letter, referring to a man who had denied the “doctrine of our faith,” he advises this gentle treatment: “Drive him away as an apostle of hell; and if he does not flee, deliver him up as a seditious man to the executioner.” “It is true that many Anabaptists suffered death merely because they were judged to be incurable heretics, for in this century the error of limiting the administration of baptism to adult persons only, and the practice of baptizing such as had received that sacrament in a state of infancy were looked upon as most flagitious and intolerable heresies” (Mosheim). In Zurich there was a place of imprisonment called the “her etics tower.” Swiss Protestants would put Anabaptists in sacks and throw them into the Rhine, remarking “That they were merely baptizing them by their own favorite mode of immersion” (Menzel).

The Calvinists were as intolerant of the Lutherans as the latter were of the Anabaptists. In some parts of southern Germany the Calvinists had gained the ascen dency and they drove out the Lutheran “sons of the devil.” “More than a thousand Lutheran ministers were proscribed, with their wives and children, and reduced to beg the bread of charity” (Olearius).

In Switzerland Calvin ruled with an iron hand. Audin tells us that the lady who arranged her hair coquettishly was to be imprisoned, as also her chambermaid; the merchant who played cards was confined in a jail; no one could have in his possession a cross or any other symbol of the Catholic church; to sell wafers was a finable offense, and the merchant s stock would be burned as sacrilegious; if a man kept his hat on at the approach of Calvin he was fined; if he contradicted Calvin he could be brought before the consistory and threat ened with excommunication; all must eat meat on Friday, because Catholics had conscientious scruples against doing so; the penalty of disobedience was three days imprisonment.

In one instance a father was imprisoned for four days because he preferred a certain name for his child and the minister preferred another. For having “proposed an opinion false and contrary to the evangelical religion,” Jerome Bolsec was exiled; Gruet was beheaded and his head nailed to a post because “he was suspected of being the author of a placard against Abel Poupin, and because letters ridiculing Calvin were found in his house”; Servetus, on the charge of being a sower of heresies, was kept in prison for two months, tormented with vermin, almost naked, and with little food, and then taken out and burned slowly to death in a greenwood fire.

This atrocious murder was sanctioned by even the “merciful” Melanchthon. Calvin published a treatise entitled “A Faithful Account of the Errors of Michael Servetus, in which it is Proved that Heretics ought to be Restrained with the Sword.” To this Castellio or Socinus replied; this in turn called out Beza and a host of smaller Protestant writers, who proved with perfect ease, of course that killing heretics was sanctioned by the Bible. They said that there was a special dispensation of providence in the case of Servetus, who might have escaped had he not gone to Geneva in disguise after his first conviction. “Calvin and other foreign divines had many tools in Poland, particularly Prasnicius, a violent orthodox clergyman. With this man, and through him with the nobility, gentry and clergy, Calvin and Beza corresponded; and many divines of Germany and Switzerland, and even the synod of Geneva, sent letters and tracts into Poland, all justifying the murder of Gentilis and Servetus and the necessity of employing the secular power to rid the world of such monsters was denied the trinity and infant baptism” (Robinson, “Ecclesiastical Researches”). The consistory of Geneva advised Prince Radzivil “to use his influence with the nobility of Poland, to engage them to treat the antitrinitarians as they would Tartars and Muscovites.”

/text from wikipedia and other resources