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The pastors in Protestant churches (Baptist, Episcopalian and Methodist) were routinely shaking down slaveholders for money to achieve mild church sanctioning. After a while, and under heavy Northern church abolitionist pressure, the Southern churches worked with the slaveholders to find moral justifications for slavery. Before that, the non-slaveholders and slaveholders alike were suffering from a dualism of conflicting ideas, while also not believing the slaveholder's claims of Christian scripture support. This psychological splitting was also tearing apart the communities. Justifying slavery, torture, abuse, etc. while also professing to be Christian proved to be a challenge.
The result was that, if the pastors were going to shake down slaveholders, the churches needed to come to the plate and devise ways to morally justify slavery to the whole South. The churches, working with slaveholders, created something called Southern Paternalism. The slaveholders were acting as good Christians by saving the slaves from the slave merchants. While the slaves were often abuses and killed, their suffering in life, along with the introduction to Christianity, would guarantee them a Christian afterlife.
This though was pushed throughout the South and became integrated within the Southern culture. Heck, the pastors had their own slaves to tend to the church properties and their own households. The investment in cheap labor was part of Southern society and they tried to say that up North, those who worked got meager wages and had an even worse private life than the Southern slaves. This, as we all know, is just another means to make their actions justified in their minds. The church and society also pushed that whites were the superior race. The sermons to the slaves reinforced the ethic to be a good slave and do your work for your masters.
England was intercepting slave ships and other cargo ships to check for slaves and this added to the anger that the North was pressuring the South to abolish slavery. The flag is part and parcel of this secessionist movement, mainly spurred by this tension.
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