CRAP: People are basically good, and will do the right thing if left to their own devices.
Alternative: Civilization has always placed restraints on human behavior, precisely because it is not true that all people are basically good. The nature of those restraints has changed dramatically -- and tragically -- over the last several hundred years. What is left barely works at all, and hints at what might be left after a total breakdown.
1. supernatural retribution, divine justice, hell
2. civil justice, police, prosecution, jail
3. keep out, no trespassing, razor wire, gated communities, walled cities