Nothing like some current psycho-social scientific research (hat tip: Zhongnanhai) to verify claims that have been around for a couple of thousand years:

Common game theory has held that punishment makes two equals
cooperate. But when people compete in repeated games, punishment fails
to deliver, said study author Martin Nowak. He is director of the
evolutionary dynamics lab at Harvard where the study was conducted.

"On the individual level, we find that those who use punishments are the losers," Nowak said his experiments found.

Those who escalate the conflict very often wound up doomed.

"It’s
a very positive message," said study co-author David Rand, a Harvard
biology graduate student researcher. "In general, the thing that is
most, sort of, rational and best for your own self-interest is to be
nice."

     Sounds Mencian to me.  We all have a heart that cannot bear to see others suffer and when we act with compassion and humanity toward others we not only fulfill out internal appetite to enact our duties but we also contribute to the creation of a better society.  It is not only right to be humane, but it is also efficacious.  The contrary, dreary Legalist emphasis on "clear laws and strict punishments" fails.

     There is, however, one caveat:

The study looked at games between equals. Punishment does seem to have
a place in games when one player is dominant and needs to enforce
submission, Nowak said.

    To get a better sense of this, let’s go to the recent Nature article:

Dreber et al. conclude that costly punishment is
a ‘maladaptive’ behaviour in social-dilemma situations — one that is
fundamentally counterproductive, because it pays off neither for the
punisher nor for the group. Thus, although it frequently induces
cooperation, it can’t have evolved for inducing cooperation. Not even
the cooperation-enhancing effect appears consistently in social-dilemma
games. In some societies, not only free-loaders but also high
contributors are punished, which dampens and sometimes even removes the
cooperation-enhancing effect of punishment⁸.

Dreber et al.
argue that punishment has evolved for another purpose, such as coercing
individuals into submission, or establishing dominance hierarchies. But
the fact remains that, given the choice, players of social-dilemma
games have been shown to prefer an environment where punishment is
possible. That preference pays off when participants, punishers as well
as non-punishers, enter this environment after the initial period of
high punishment is over and cooperation dominates⁴.

   This suggests that, in the early phases of social interactions, where each side is looking to dominate or gain significant advantage over the other, punishment may play a role.  But punishment does not, over time, contribute to social cooperation. The persistence of punishment thus may signal an obsession with "maladaptive" domination and an ignorance of how to build social cooperation.  As the Nature article puts it:

Thus, it would seem, winners don’t punish; and punishers perish.

 Which has a certain Confucian-aphoristic resonance…