Miz--
It comes to this: fundamentally, we're still animals. We tell ourselves that we can extend our moral sensibilities beyond our little tribal groups, and, to a limited extent, we're successful. We base societies-- civilizations!-- on the idea that we can and should live together without being complete shits to one another.
Inevitably, this is to some degree wishful thinking, and to some degree a lie. It's true almost, but not quite, to the extent that we manage to honestly persuade ourselves of its truth.
But in the end, we are still built for small villages and family groups, and can, will, and do edit anyone outside of that circle out of the zone where conscience applies, leaving hardly a ripple.
It is pointless to blame humanity for not meeting the ideals it sets itself. It remains a species of overly clever, murderous tribal apes trying to be something more civilized. Only in our very best moments do we seem to come close to success.
Maybe we'll be more than that some day. Maybe. I'm not holding my breath.
Aside from LeGuin, I also recommend Vonnegut for his nuanced thoughts on our tragicomic species. Deadeye Dick for the human "comedy" of errors, Slaughterhouse 5 for thoughts on human life, death, and morality, and the weight of each in the face of the horrors we inflict on ourselves and each other (Pooteeweet?), and Galapagos for a sadly hilarious take on our place in the world, the source of our miseries, and a possible, er, solution.
I think that, aside from finding at least one human being I decided was entirely worthwhile, cancer on the planet or no, it was Vonnegut that did the most to make me fall out of love with apocalypse.