“Wise souls are not humane.” To that, Le Guin writes:
The “inhumanity” of the wise soul doesn’t mean cruelty. Cruelty is a human characteristic. Heaven and earth—that is, “Nature” and its Way—are not humane, because they are not human. They are not kind; they are not cruel: those are human attributes. You can only be kind or cruel if you have, and cherish, a self. You can’t even be indifferent if you aren’t different. Altruism is the other side of egoism. Followers of the Way, like the forces of nature, act selflessly.
(Emphasis mine.) By other side, Le Guin is invoking the yin/yang structure that recurs throughout the Tao. That is, altruism and egoism are two sides of the same coin, each of them giving rise to the other. This is not quite the same as saying they are opposites, although that is also true: it’s that each contains the other. They are interconnected, interdependent. An act of altruism may attempt to subvert the self but the ego stubbornly remains, ready to accept the reward. A true act of selflessness (which I think Le Guin would concede is possible but very rare) would be unaware of itself: there’d be no self to register the lack of it.
