I think I heard that in the history of Rome podcast. The father gives contradictory advice until the end where the moral of the story is revealed. Which is that he should either free everyone so as not to create enemies or kill everyone as not to leave any enemies alive. Anything in between will leave enemies plotting for revenge.
That's my best recollection of the story. I'd appreciate either which story this is, a link to Wikipedia or to the podcast episode. Thanks.

