You are dancing around the issue without realizing it by focusing on "big" societies. Humans are social creatures, but only up to a certain extent. We like our tribe of a few hundred people and that's about it. When a society gets bigger than that, our brains naturally find ways to discriminate to create an "us" and a "them". Simply put, big societies are bad societies. Agriculture was a mistake (also because grain and an excessively convenient source of calories is bad for us).

Unfortunately there's no solution for this, outside of any number of apocalypse scenarios. But we can mitigate the worst of the issues by destroying the very idea that a greed or privilege-based society is permissable.