It feels weird writing this, but I think Žižek may be onto something. Kim Ki-duk may have intended his film to be a straight depiction of Buddhist asceticism, but you get the sense that the austerity being portrayed is just as brutalizing as life in the secular world. The monk warns his ward that lust leads to possessiveness, jealousy and murder. But the tranquil world of the temple is shown to have its own strictures, that possess the minds of its inhabitants. There are doorways without walls, which the characters continue to respect and use – just as they cling to the traditions and morality they have grown up with.
The boy finds an cruel kind of pleasure in exercising his power over animals, only to turn that same will-to-power back on himself when he grows up – mortifying his body in order to cleanse his mind. Kim may be suggesting that the boy would have become a killer even if he wasn't a monk, and that religion has been a way to atone for his crimes. I wonder whether the socialisation available in the big bad world isn't a better way to curb violent tendencies.