I've rewritten the introduction to "Traditional Religions and Abolition of the Slave Trade" by Vexen Crabtree
Voodoo priests, slave protests and economics were the three powerful factors that brought the age of slavery to an end. They battled against organized campaigns that aimed to keep the trade going, with religious justifications centering on the Christian Bible. Christianity and Islam were the two worst-offending religions, and conservative Christians hung on to their slaves for the longest. China never ordained slavery, and the Buddhist
Emperor Wang Mang was "probably the first recorded ruler to abolish the slave trade". There are some early anti-slavery thinkers, such as the pagan Zeno's Stoics
), but as there are so few anti-slavery movements until much later, this page simply concentrates on the movements that existed at the time when the major slave trades of the world ceased to operate.
And added a bit:
6.4. Christian Pro-slavery
Christians with vested interests justified slavery on account of their religion although the Bible is much less openly embracing of slavery than the Qu'raan. Christian arguments were used such as slavery facilitated the evangelizing of slaves, that black couldn't be saved anyway, and that certain Biblical stories made blacks out to be inferior and cursed by god - although no scholars nowadays interpret these passages in this way, at the time, they did. Bishops and Monks provided some of the arguments that were used all over to justify the ownership of slaves. The fact that god-worship does not lead to better morals in society is one of the factor that leads skeptical and atheist thinkers such as Victor Stenger to conclude that God doesn't exist:
“Jesus had many opportunities to disavow slavery. He never did. St. Paul reaffirms the practice: "Bid slaves to be submissive to their masters and to give satisfaction in every respect" (Titus 2:9).
Prior to the Civil War, the Bible was widely used to justify slavery in the United States. Baptist leader and slave owner Richard Furman (d. 1825) laid the foundation for the biblical arguments that would be made in support of slavery leading up to the Civil War. While president of the State Baptist Convention, Furman wrote to the governor of South Carolina, "The right of holding slaves is clearly established in the Holy Scriptures, both by precept and example". [...]
While Christians in the South held onto their slaves as long as they could, secular humanist Richard Randolph of Virginia began freeing his in 1791. Popes and other fathers of the Catholic Church owned slaves as late as 1800. Jesuits in colonial Maryland and nuns in Europe and Latin America owned slaves. The Church did not condemn slavery until 1888, after every Christian nation had abolished the practice.”
"God, the Failed Hypothesis: How Science Shows That God Does Not Exist" by Prof. Victor J. Stenger (2007)