Our innate understanding of reciprocity is severely limited by our social identity though; it's much easier to empathize with in-group members than with an out-group member. To reciprocate with an out-group member requires considerable training.
So I think the GP is correct, once a society encompasses multiple distinct tribes, it is easier to "guide" people with (threats of) in-group punishment than with out-group empathy.
Not true at all. An out group hits me, innately I want to hit back. An out group shows me empathy innately I show it back. You would have to learn otherwise.
The in-group out-group is some higher part of the brain that rationalised our values.
So I think the GP is correct, once a society encompasses multiple distinct tribes, it is easier to "guide" people with (threats of) in-group punishment than with out-group empathy.