Sources abound. This is a timeline of Calvin's life which all should read.
In this part of his life Calvin gives reasons why he persecuted others:
IF he was a Christian, this cannot be defended.
In this part of his life Calvin gives reasons why he persecuted others:
http://www.a-voice.org/tidbits/calvinp.htmPrefatory Address in his Institutes to Francis, King of the French, 1536. "But when I perceived that the fury of certain bad men had risen to such a height in your realm, that there was no place in it for sound doctrine, I thought it might be of service if I were in the same work both to give instruction to my countrymen, and also lay before your Majesty a Confession, from which you may learn what the doctrine is that so inflames the rage of those madmen who are this day, with fire and sword, troubling your kingdom. For I fear not to declare, that what I have here given may be regarded as a summary of the very doctrine which, they vociferate, ought to be punished with confiscation, exile, imprisonment, and flames, as well as exterminated by land and sea. This, I allow, is a fearful punishment which God sends on the earth; but if the wickedness of men so deserves, why do we strive to oppose the just vengeance of God?"
IF he was a Christian, this cannot be defended.