4 ideas
Anton, an Earth historian disguised as the nobleman Don Rumata, spends years in Arkanar obeying a strict non-intervention rule while Don Reba's gray troopers and then the militant Holy Order hunt down the kingdom's literate people. Colleagues later follow a trail of corpses to find him, and he is withdrawn to Earth, unable to fully explain or live with what he did.
Mediocre, resentful functionaries (the 'gray') who seize power by purging the educated do not become the final regime. By destroying the competent and the independent, they empty the field for a more disciplined and fanatical force (the 'black' Holy Order), which uses them and then replaces them. Supporting the gray as a lesser evil therefore prepares the way for the greater one.
When Rumata asks the healer Budakh what he would do if he were omnipotent, each proposal fails once it is tested. Giving everyone bread breeds dependence and new masters, forcibly making people good strips them of agency, and remaking them entirely erases the humanity it meant to save. Budakh finally asks the god to leave them to find their own way, which shows that power to fix a society from outside cannot produce the society it aims at.
A rule of pure observation assumes the observer stays unchanged, but watching atrocity without acting forces the observer to adopt the cruelty, drunkenness, and contempt of the role he performs. Over time his restraint becomes either complicity or suppressed rage. Seen this way, a detached stance in the presence of evil does not stay neutral: it reshapes the one who holds it until it gives way.