That might be the lore of the novel, but calling it "earth humanitarian values" is both a cop out, and very flawed, if anything you could make the argument that many people on earth today are just as brutal if not moreso than in ancient times, we just have much better tools to kill people with and much better ways to keep them in line, and in the long run "humanitarian rules" led to situations like isis springing up not to mention that the death penalty's actual purpose is to prevent more bloodshed, not cause more bloodshed, the argument is honestly the thing i hate most about japanese manga these days, it's too unrealistic, "oh that general likes to rape and pillage kingdoms, sending him back alive or even just imprisoning him, a guy who's a walking disaster, is a good idea, what he broke out and burned down another kingdom? time to arrest him again", or as i call it the batman paradox, how many lives would be saved if batman just picked up a gun and shot the joker, stuff like that.