Yes, I knew that Africans were complicit in slavery. But you are justifying. I am merely stating that at a point in time the constitution did not acknowledge some people as humans, and it is a living document, hence amendments. There are many persons such as Emmanuel Kant, to whom I admired for his ethical writing, but who were racist because of the time. The corollary, there were white European like Wilberforce who fought against racism. There are not too many civilized people remaining who are still justifying slavery.