[Ed. Note] As we read this article, keep in mind that one of the most basic ways of determining whether or not something is truly Christian is whether it is done in the loving, compassionate, and peacemaking ways of the teachings of Jesus Christ. He also taught that capital punishment was wrong by the way He responded with the woman caught in adultery. The shedding of blood can never be Christian.
Bernard of Clairvoux was teaching that "pagans are not actually humans". It is very sad that beautiful France produced that monster - so many pagans had been killed because of his crazy sermons:
“The Christian glories in the death of the pagan… To inflict death or to die for Christ is no sin, but rather, an abundant claim to glory. In the first case one gains for Christ, and in the second one gains Christ himself. The Lord freely accepts the death of the foe who has offended him. The knight of Christ, I say, may strike with confidence and die yet more confidently, for he serves Christ when he strikes, and serves himself when he falls. Neither does he bear the sword in vain, for he is God's minister, for the punishment of evildoers and for the praise of the good. If he kills an evildoer, he is not a human killer, but, if I may so put it, a killer of evil. He is evidently the avenger of Christ towards evildoers and he is rightly considered a defender of Christians. Should he be killed himself, we know that he has not perished, but has come safely into port. When he inflicts death it is to Christ's profit, and when he suffers death, it is for his own gain” (St. Bernard of Clairvaux, De Laud Novea Militae - In Praise of the New Knighthood).
Later Sorbonne (Paris University) developed ideology of crusades against Poles, Lithuanians, Russians and pagans. Sorbonne genocidal ideas were based on the scholastic doctrine of tyrannicide developed by John the Little (Jean Le Petit, Johannes Parvus). Jean Le Petit wrote “Quilibet tyrannus”. Some time later in Sorbonne Dominican Johannes Falkenberg applied the doctrine of tyrannicide to pagans and heretics demanding in all seriousness that all “tyrants” - Poles, Lithuanians and Russians - should be totally exterminated. “The Emperor has the right to slay even peaceful infidels simply because they are pagans" said Johannes Falkenberg of Sorbonna.
Quite similar was the case of Johann von Falkenberg, a German Dominican, who had maintained in a violent work against the King of Poland that it was allowed to kill him and all other Poles (Mansi, Conc., XXVII, 765). Many demanded with much earnestness the condemnation of Falkenberg, but no definite sentence was pronounced, despite the ardent discussions (see Tyrannicide), not even in the forty-fifth (last) session when the Poles urged it on Martin V; he declared that in matters of faith he would approve only what had been decided by the holy general council conciliariter, i.e. by the whole council and not by one or more nations.
Many of the Reformers were more or less in favour of tyrannicide. Luther held that the whole community could condemn the tyrant to death (Sämmtliche Werke", LXII, Frankfort-on-the-Main and Erlangen, 1854, 201, 206). Melanchthon said that the killing of a tyrant is the most agreeable offering that man can make to God (Corp. Ref., III, Halle, 1836, 1076). The Calvinist writer styled Junius Brutus held that individual subjects have no right to kill a legitimate tyrant, but that resistance must be authorized by a representative council of the people (Vindiciae contra Tyrannos, p. 45). John Knox affirmed that it was the duty of the nobility, judges, rulers, and people of England to condemn Queen Mary to death (Appellation).