op, in most flavors of christianity keeping slaves is not only disallowed, but also evil. so much so, the french had to explicitly create an entirely new type of christianity (baptism) because the pope forbade them from using enslaved african converts. the roman catholic church *also* forbade mass migration of blacks because the local indians, most of whom were converted to catholicism, could not be enslaved. this was a known problem and is why the subsequent agreement between the jews and anglos that would become the southern gentry was evil by most accounts. americans tolerated it because the tobbacco and cotton money was good and financed the united states, until the industrial revolution happened. at that point, a large portion of white europeans and americans became literate and could read the bible. this was when most decided that slavery was evil and needed to be fought. as in, fought with guns. by shooting people. by the time the underground railroad was a thing, bleeding kansas and open warfare between abolitionists and slavers was underway. not small fighting, but real-world terrorism forcing an extended (and failed) government military operation to police it. this would ultimately lead to the caning of charles sumner, john brown's raid on harper's ferry, the execution of john brown, and the election of republican abraham lincoln by the supreme court. the ur itself was financed by wealthy northern industrialists, members of the republican party, as slaves could be taken to safe areas and hidden behind their lawyers and (after the south seceded) the federal army itself. others were moved up to canada, although canadian laws about it were stringent (eg requiring literacy) because even the british king didn't want niggers in his country.
United States