"Natural" morality leads from sensory feelings of pleasure and pain. E.g. don't hurt others. "Man-made" morality may overlap "natural" morality, in the sense that we have laws that codify our natural instincts. E.g. assault and battery. But "man-made" morality also can involve things that do not necessarily lead from our sensory feelings of pleasure and pain. For e.g., it is wrong not to pay your taxes.
Just as one can break a man-made moral code, one can break a natural moral code. Yes, the child being spanked is feeling pain, but the parent can ignore the natural moral code not to do that - as with all criminals.
The notion of intent. A justicial notion; invoking the idea of a free agent, choosing to follow a motive "outside" of morality.
It would seem like we would avoid being hurt, but I don't see the leap to other people's pain, nor do, it seems, animals. The ones that do care about other animals, generally, but not limited to their own species might have affection as a motivating factor or empathy.
Empathy, of course. You imagine the pain you are inflicting on another and feel pain as a result. This is "natural" morals and conscience.
The text you quoted isn't Buddhist, mind you. But yes - Buddhism could be called "egocentric". However, this is not necessarily negative.
