Why Is It Wrong to Harm People?

On a naturalistic worldview, inflicting harm upon other members of our species is really wrong. I'm capable of appreciating reasons for respecting your property that my one-and-a-half-year-old nephew doesn't have the capacity. There are differences between people that allow me and you to think about our behaviors. It's precisely because they lack that capacity that makes no sense that the notion of right and wrong behavior gets no purchase.