There's an entire section of the Bible about slavery, and another section endorsing it. Also, the Civil War did NOT happen because of slavery. That is a widespread misconception that for some reason is still taught.

"It was entirely a consequence of the Southern states' secession, which occurred despite the undeniable fact that the slave states could not have hoped for better protection of slavery than that afforded by the U. S. Constitution — provided they remained in the Union. Both Lincoln and the slaveholders well knew in 1860 that a constitutional amendment ending slavery would never be mathematically feasible. But Lincoln further understood that the South was gravitating toward secession as the remedy for a different grievance altogether: The egregiously inequitable effects of a U. S. protective tariff that provided 90 percent of federal revenue.

Foreign governments retaliated for it with tariffs of their own, and payment of those overseas levies represented the cost to Americans of their U. S. government. Southerners were generating two-thirds of U. S. exports, and also bearing two-thirds of the retaliatory tariffs abroad.

The result was that that the 18.5 percent of America's citizens who lived in the South were saddled with three times their proportionate share of the federal government's costs." quoted from this

And as far as all the bad shit we've done, it really isn't that high on the list. Considering we have killed off and stole from the Natives we took the country from, we've overthrown many foreign governments to suit our own interests (usually for money or power), and on a regular basis in modern times we encourage corruption in our own government while talking shit on other countries for the same thing.