wikipedia:
"Slavery in different forms existed within Christianity for over 18 centuries."
This statement has no citation on wikipedia and is misleading because it assumes that Christianity is somehow a political institution.
"By the end of the Medieval period, enslavement of Christians had been largely abolished throughout Europe although enslavement of non-Christians remained an open question. "
In response to this and other misconceptions I submit:
"Some historians deny that there ever was an end to medieval slavery-that nothing happened other then a linguistic shift in which the word "slave" was replaced by the word "serf." Here it is not history but historians who are playing word games. Serfs were not chattels; they had rights and a substantial degree of discretion. They married whom they wished, and their families were not subject to sale or dispersal...While no one would argue that medieval peasants were free in the modern sense, they were not slaves, and that brutal institution had essentially disappeared from Europe by the end of the tenth century. Although most recent historians agree with that conclusion it remains fashionable to deny that Christianity had anything to with it...Rather, slavery is said to have disappeared because it became an unprofitable and outdated mode of production...Hence the claim that the end of slavery was not a moral decision but one of pure self-interest on the part of the elite...That same argument has been made concerning the abolition of slavery in the Western Hemisphere. Both claims are consistent, of course, with Marxist doctrine but are quite inconsistent with economic realities. Even as late as the start of the American Civil War, Southern slavery remained a very profitable 'mode of production.' The same was true in early medieval Europe....Slavery ended in Europe only because the church extended its sacraments to all slaves and then managed to impose a ban on the enslavement of Christians (and of Jews). Within the context of medieval Europe, that prohibition was effectively a rule of universal abolition."
He goes on to talk about Ephesians 6:5,8 and how people forget to quote the next verse which is "Masters, do the same to them (slaves), and forbear threatening, knowing that he who is both their Master and yours is in heaven, and that there is no partiality with him." More: "At the end of the eighth century, Charlemagne opposed slavery, while the pope and many other powerful and effective clerical voices echoed Saint Bathilda. As the ninth century dawned, Bishop Agobard of Lyons thundered: 'All men are brothers, all invoke one same Father, God: the slave and the master, the poor man and the rich man, the ignorant and the learned, the weak and the strong...none has been raised above the other...there is no...slave or free, but in all things and always there is only Christ.' At the same time, Abbot Smaragde of Saint-Mihiel wrote in a work dedicated to Charlemagne: 'Most merciful king, forbid that there should be any slave in your kingdom.' Soon, no one 'doubted that slavery in itself was against divine law.'" This last quote comes from Marc Block Slavery and serfdom in the Middle Ages. All of this quoted from Rodney Stary The Victory of Reason pp. 26-30.