The rules of society you mentioned here are plain sanity constraints. If we allow the value of human life to drop then lots of people will fall victim to flawed systems and madmen aiming to capitalize on the change. Think about Hitler and the Jews or genocidal african tribes - they allowed themselves to think they had the right to murder people with little justification. Imagine a world where obese, dumb, handicapped and unseemly ugly people are shot on sight, because their being a burden on society is considered more important then their right to live - regardless of their ability to work. And what if a flaw in the system was to flag you as retarded for your opinions ? Humans are way too imperfect to make such decisions, which is why the society fights anyone questioning these values.