When bad people are alive, you can oppose them. But as soon as they are gone, they're not your enemies any more. They're just people who once were, but now are not. Memories.
The quote - there are no enemies in death - comes from "Lone Wolf and Cub," a favorite serious of mine. You can see me reviewing a bit of it at the entry "Rule an Empire, Fistful of Rice."
After some mortal enemies is vanquished, the protagonist gives them a respectful burial. When asked why, he explains that there are no enemies in death.
It's easy to get caught up in cheering for one side of history, but your feelings don't affect what's already happened. And strong feelings can easily blind you from figuring out what really happened.
It may not always be possible, but it would be good for you if you can become dispassionate in analyzing long dead eras.
Question from a reader --
"Quick question (maybe not quick answer)
Some people that are very successful attract respect and devotion. Other people that are very successful attract jealousy. What's is the difference in the behaviour of the successful individual?
If I want to succeed in the long run, I prefer the former.
My guess. Maybe humility and value sharing play a part... or is this something not to be concerned about?