A. There is nothing "idiotic" about looking at actions people have taken in the past in the light of more recent moral and philosophical developments.  Arguing that people should have been expected to act in accordance with modern morals is problematic, but there is nothing wrong with saying that Liu Bei was a bad person for his actions, even if his contemporaries may not have agreed.    B. The idea that everyone 200 years ago was an idiot or a monster or anything similar is absolutely ridiculous, and ironically reflects a pretty gross level of presentism.