It not so much a thing of "passing judgement" by one generation upon another so much as it is a understanding of our Grandfathers place in history, and our place in history. Slavery in 1860 was the political/social/moral question of that day. Today it can be a number of simular issues, the enviroment, global warming, abortion, the price of gasoline, immigration.

The point is that we can not imagine which of those political/social/moral issues will become the revulsion of our great-grandchildren's enlightened understanding in their day. Are we wrong today because we drive our cars for example? It is something that we take for granted every day. It is our way of life. Just the same as Slavery was their way of life.

Likewise I am as morally opposed to abortion today as the Abolishionist were morally opposed to slavery then. But, we haven't gone to war to correct what I view as a moral wrong. And if we won't go to war to correct our present day morality issue, why do we think that their morality issue of 1860 was the primary cause of the conflict that erupted in 1861?

On the other hand maybe our Great-Grandchildren's understandings will have no basis in morality as we define it today, and may not care what we have done. They may even reinstate slavery, for example, because it is still a common practise in some part of the world today.