From A Libertarian Replies to Tibor Machan’s “Why Animal Rights Don’t Exist”:
I find it strange that so many of my fellow libertarians and anarchists oppose and ridicule animal rights with such passion. For one thing, an animal right is perfectly libertarian in that it is a negative right. Unlike incoherent positive rights, such as the “right” to education or health care, the animal right is, at bottom, a right to be left alone. It does not call for government to tax us in order to provide animals with food, shelter, and veterinary care. It only requires us to stop killing them and making them suffer….
[I]t is immoral for moral agents to treat animals in ways we would not treat human marginal cases [e.g., infants or Alzheimers sufferers] except in self-defense. Because animals are not moral agents, what they do is outside the purview of ethics.
And that (fine essay), you see, is why even if we humans had evolved to eat a high-fat, Paleolithic-like diet, the morally right thing to do would still be to go vegetarian. And ironically, the very thing which most separates us from the animals—our ability to reason—and which supposedly gives us a unique right to life which other animals don’t have, is what drives us to that conclusion.
There may indeed be crazies in the animal-rights movement who assert that “we have no right to our own lives and that we must sacrifice our welfare for the sake of creatures who cannot think or grasp the concept of morality.” But those are not our only choices, even today: As John Robbins and others have been proving for the past twenty to forty years, our species can live perfectly well on a vegetarian diet. (Our Paleolithic ancestors who ate a high-fat diet were not only much more active than we are, they also had a life expectancy at puberty which was only two-thirds of what ours is today. It is no accident that the artery-blocking and other debilitating effects of a meat-heavy diet only start to show in the final third of our lives today: we have “evolved” to eat that diet only to the extent to which we’ve also evolved to live only into our mid-fifties.)
So, as far as animal suffering “necessary to support human needs,” there actually isn’t any (at least in terms of diet; medical research is a different story).
And if vegetarians take more vitamins, and thus consume more (refined) plants in that than do meat-eaters, it’s nothing compared to the ten or more pounds of grain (and however many gallons of water) which go into producing one pound of beef. On a planet with finite natural resources, there are moral/environmental issues which come up in that, too.
And as far as it being “staggering that anyone could dedicate their efforts to animals” while children are starving to death in the developing world, etc.—an argument which I assume Bernie Planck doesn’t find convincing 
—you can make similar arguments about anything other than fighting against the most important threat to Western civilization. Teaching Intelligent Design in the science classroom? It’s a small issue compared to jihad or to the life of a Third World child, right? So just let it slide. (Yes, I have actually seen that argument made on classical liberal sites.)
Gay marriage? Same thing: Will any child die if a couple of fags/lesbos can’t get married? By contrast, if any gay-rights activist could save a child’s life by focusing his or her energies on Third World children instead of on gay marriage in North America, shouldn’t they feel morally bound to do that instead?
You don’t have to go far at all down that path before the Western Civ you’re trying to preserve has already been lost … to the crazies on the Christian side of the spectrum, who have life-or-death, soul-saving religious reasons and motivations to reform a secular world in which science, reason and sexual (etc.) freedoms matter, into one in which they don’t.
If you don’t fight every battle as if it was the most important one, the one thing you can be sure of is that you’re going to lose it. Simple as that.
Plus, it’s not as though the concern for the welfare of animals excludes caring about infants in the developing world, and actually doing something about it. Or why is it that many of the same people who care enough about the welfare of animals to switch to a vegetarian diet for that reason, are also the ones who boycott Nestlé products?
