@ponderable saidOr, at an individual level:
There can be no keener revelation of a society's soul than the way in which it treats its children.
Nelson Mandela
"The true measure of a man is how he treats someone who can do him absolutely no good."
— Samuel Johnson
and
"He never yet no villainy ne said
In all his life, unto no manner wight.
He was a very perfect gentle knight."
— Geoffrey Chaucer
and, reputedly,
"I don't trust anyone who's nice to me but rude to the waiter. Because they would treat me the same way if I were in that position."
— Muhammad Ali
(and, of course, Luke 18:16.)