This is my John Galt speaking cartoon

[eppie]

Hi,

A common fault in these types of discussions is to hold people of the past accountable to our present morality and fault them for their failure to live up to a moral code that they never ascribed to. And to compare moral codes is, ultimately, a foolish thing. Most moral codes are a mixture of superstition, prejudice, and pragmatism.

Human failures are funny things; the more remote, the more clearly seen. We have no problem seeing the evils committed throughout history and the wrongdoings of distant rulers. But we seem be blind to much of our own evils and wrongdoings.

--Pete

Well of course, but this isn't the whole story. In the 1940's it wasn't a common way of thinking that committing genocide was a good thing.
The same for the native americans. Columbus might have thought they were a lower form of humans, but murdering tribes of indians in the end of the 19th century is another thing.

Of course you can't hold the old romans moraly repsonsible for killing germanic tribes, but, and this is very important, you can hold people responsible for crimes that even at the day the were commited were already considered wrong by the greater community. And that is where the learning and teaching comes in. You can learn from how groups of people are swept up by some charismatic leader to commit crimes that also in that day and age were considered as horrible and wrong.