Just finished, and the treatment of slavery (other than no mention of my largely insignificant ancestors who fought) is probably my biggest complaint. We all are hopefully in pretty much unanimous agreement that slavery was abhorrent and is one of many blights that was rightfully exposed in this documentary. I want to be clear on that point because reactionary Surly can be reactionary, but most of the southern slave holding founding fathers where in a serious pickle when it came to slavery. Slaves represented a significant capital investment, and were often leveraged. Even if they were serious about ending the practice, and few were dedicated enough to jeopardize their lifestyle for the cause, most of them didn't have the financial means. They were cash poor and land rich. It'd be like a modern farmer just deciding that he should buy out the bank for all of his tractors, outbuildings, and other equipment.
Slavery was not particularly economical at the time. You had to feed, house, and clothe a labor force that remained idle for significant portions of the year. It seemed like it was an institution that would die a natural death and hopefully not ruin them financially to most of the founding fathers who were slaveholders. They were happy to kick the can of horrific human subjugation down the line. La Fayette was one of the few who put his money where his mouth was and actually purchased a plantation with slaves with the intent to free them.
But then came along Eli fucking Whitney with his fancy cotton gin and made slavery economical again...