What I'm saying is that rational people can look at the history of societies and how they functioned and use that as a basis for their own rulemaking. Not surprisingly, functional societies (the US, Japan, Monaco) end up having many of the same rules while dysfunctional societies (Somalia, Zimbabwe) do not.
You don't need religion to tell you that a society that allows people to kill each other without consequences is one no rational person wants to live in.