Historical figures should not be judged by modern standards

lndeed...*darts eyes quizzically*.

They should, and they shouldn't.

You can't understand historical figures without understanding how different their mindsets were from our own, a modern person can't understand the actions of historical figures without understanding their motivations - which may include strong beliefs in the Divine Right of Kings or infant damnation or the property rights of slave owners, and other crap that's been left on the dustheap of history.

On the other hand, slavery is still wrong by any standard, and monarchs don't actually have the mandate of heaven. Everyone judges everyone else by their own standards and within the context of their own culture, that's just human nature. It's not going to stop.