Here is Packer, in an essay entitled "John Calvin and Reformed Europe," commenting on Calvin and Servetus:
The anti-Trinitarian campaigner Servetus was burned at Geneva in 1553, and this is often seen as a blot on Calvin's reputation. But weigh these facts:John Piper, in his biographical address on Calvin (published in The Legacy of Sovereign Joy), devoted an appendix to the issue, entitled Calvin's Barbaric World – The Case of Michael Servetus. Here is how he concludes:So the times were harsh and immoral and barbaric, and had a contaminating effect on everyone, just as we are all contaminated today by the evils of our time. Their blind spots and evils may be different from ours. And it may be that the very things they saw clearly are the things we are blind to. It would be foolhardy to say that we would have never done what they did under their circumstances, and thus draw the conclusion that they have nothing to teach us. In fact, what we probably need to say is that some of our evils are such that we are blind to them, just as they were blind to many of theirs, and the virtues they manifested in those times are the very ones that we probably need in ours. There was in the life and ministry of John Calvin a grand God-centeredness, Bible-allegiance and iron constancy. Under the banner of God's mercy to miserable sinners we would do well to listen and learn.The burning should thus be seen as the fault of a culture and an age rather than of one particular child of that culture and age. Calvin, for the record, showed more pastoral concern for Servetus than anyone else connected with the episode. As regards the rights and wrongs of what was done, the root question concerns the propriety of political paternalism in Christianity (that is, whether the Christian state, as distinct from the Christian church, should outlaw heresy or tolerate it), and it was Calvin's insistence that God alone is Lord of the conscience that was to begin displacing the medieval by the modern mind-set on this question soon after Servetus' death.
- The belief that denial of the Trinity and/or Incarnation should be viewed as a capital crime in a Christian state was part of Calvin's and Geneva's medieval inheritance; Calvin did not invent it.
- Anti-Trinitarian heretics were burned in other places beside Geneva in Calvin's time, and indeed later--two in England, for instance, as late as 1612.
- The Roman Inquisition had already set a price on Servetus' head.
- The decision to burn Servetus as a heretic was taken not only by Calvin personally but by Geneva's Little Council of twenty-five, acting on unanimous advice from the pastors of several neighboring Reformed churches whom they had consulted.
- Calvin, whose role in Servetus' trial had been that of expert witness managing the prosecution, wanted Servetus not to die but to recant, and spent hours with him during and after the trial seeking to change his views.
- When Servetus was sentenced to be burned alive, Calvin asked for beheading as a less painful alternative, but his request was denied.
- The chief Reformers outside Geneva, including Bucer and the gentle Melanchthon, fully approved the execution.