I think society adjusts itself to the level of barbarians present.
It always lags though, so mismatches occur (same concept as generals preparing for the last war). Barbarians beget fear.
On the other hand I can see that to some extent, barbarian level adjusts itself to fit expectations of society. For example, some thieves/rapists/axe murderers/(communists/hippies/florists) became so because of parents who used extreme measures to prevent them from becoming so. So fear begets barbarians.
The preference of course is to have a society without barbarians.