With thanks to our bon ami, the knight4mary:
"The only way to argue with a blasphemer is by running your sword through his bowels, as far as it will go."
St. Louis IX, King of France
"I entirely detest heretics, and as Magistrate do promise assiduously to perform my duty in investigating them. Heresy is a kind of treason, and if a heretic persisteth in his false belief, he may be handed over to be burned."
St. Thomas More
"If heretics be altogether uprooted by death, this is not contrary to Our Lord's command."
St. Thomas Aquinas
"Error will never be suppressed unless the criminal elements of depravity be consumed in flames."
Pope Clement XII
"That it is against the will of the Spirit to burn heretics at the stake is condemned as false." Pope Leo X
"Even if my own father were a heretic, I would gather the wood to burn him at the stake."
Pope Paul IV
"With regard to heretics, two arguments must be observed: one concerning themselves, the other from the aspect of the Church. On their own side, there is the sin whereby they deserve to be separated from the Church by excommunication, but also to be severed from the world by death. For it is a much more serious matter to corrupt the faith which gives life to the soul than to counterfeit that which supports temporal life. Wherefore, if counterfeiters and other evil-doers are immediately condemned to death by the secular authorities, there is much more reason for heretics, as soon as they are convicted of heresy, not only to be excommunicated but even put to death. On the part of the Church, however, there is mercy, which looks to the conversion of the wanderer; wherefore, she condemns not at once, but "after the first and second warning", as the Apostle directs (Titus 3:10). After that, if he is still stubborn, the Church, no longer hoping for his conversion, looks to the salvation of others by excommunicating him and separating him from the Church; and, furthermore, she delivers him over to the secular tribunal, thereby to be exterminated from the world by death."
St. Thomas Aquinas