Tigers do not naturally jump through hoops on cue. Wong's interpretation is a significant contribution to our understanding of Xunzi for at least two reasons. First, it answers Munro's objection. Now, though, I wonder whether Wong needs to disagree with me at all. I take it that Wong accepts Nivison's suggestion that humans have a capacity to come to regard things as morally binding.
Human nature is what is innate in humans.
Notice, however, that if approval overrides desire in this strong sense, there must be some basis for approving of an action other than its relation to the satisfaction of desire. Kant, of course, held that pure practical reason yielded the categorical imperative, which applies to all rational agents regardless of the content of their particular desires and emotions. Nor can Xunzi hold that the mind can act on an approval based on perception of irreducible moral properties, because he does not think there are such properties. I also agree that Xunzi's worldview is very different from that of Kant in many important ways. There is nothing corresponding to the noumenal-phenomenal distinction in Xunzi.