Don't let them off that easily. The Indians practiced slavery themselves; the Europeans didn't introduce the concept. So did the African kingdoms, who were the front end of the slave trade. Yes, it's unfortunate that Europeans imported African slaves to the Americas, because it has created problems that we're still trying to sort out. Yes, it is unfortunate that the southerners didn't pick their own cotton. But slavery was a universal human institution. The only unique thing about the Europeans is that some of them, in the mid 18th century, set about trying to abolish it.
Good points !!!