I don't know if I agree with this 100%, although I think I might. In 2004, when the discovery of the Homo floresiensis was being publicized, I was fascinated by it. I was especially blown away by the idea that it lived as recently as 12,000 years ago, and, according to some local lore, possibly much more recently. It almost certainly wasn't true, but it got me thinking- what if, in some remote jungle, a proto-human species still existed? After all, several variants of man existed at the same time. It requires a suspension of disbelief, obviously, but: what if?
What would we do if we found them- a small, isolated, cloistered tribe, maybe pre-lingual, stone age? Do we leave them alone? Study them? Put them in a zoo? Try to "modernize" them? I don't have an answer here, but what is certain is what we would not do: eat them. Similarly, I think a lot of use have a revulsion to eating a monkey or a gorilla. I might, but it would be weird, and not "exotic". It would be uncomfortably close to cannibalism, and eating a floresiensis even closer.
So, then, where does it end? At what point do I draw the line. I was re-reading Gombrowicz's Diary, 2nd Volume, the other day, and he was telling a story of walking on the beach and seeing a beetle flipped in the sand, struggling to right itself. Witold flipped it to its feet, and then saw another, and did the same, and the pattern kept repeating itself.
But I knew this could not last forever- for it was not just this beach, but the entire coast, as far as the eye could see; it was sown with them so there had to come a moment when I would say "Enough!" The first unrescued beetle would have to happen, too. Which one should it be? Which one? Which one? Each time I said "this one"- I save it, unable to bear that awful, almost vile arbitrariness- because why this one, why this one? Until I finally broke down, suddenly, easily, I suspended my empathy, stopped, thought indifferently, "Well, time to go back," and left. But the beetle, the beetle I stopped with, remained behind thrashing its little legs (all this was a matter of complete indifference to me now, as if I had grown disgusted with the game- but I knew this indifference was imposed upon me by the circumstances and I carried it within me like a foreign object).
I feel a lot of sympathy with this, and I think it relates to the discussion above (of course I do- why would I put it in otherwise? Well, maybe to introduce people to my beloved Gombro, but I try not to be that random). Our sympathy toward animals does have a very sudden and mostly arbitrary line. I don't like animals being tortured or maimed or treated horribly for my pleasure, but I do love eating meat. All of it, really. But I recoil in horror at the thought of eating a gorilla, a monkey, or a hobbit.
I think that as a species we are constantly, if slowly, expanding our circles of sympathy. As Elizabeth points out, not too long ago her new son, who is cognitively challenged, would have been "unworthy" of kindness, and discarded. We've opened that circle, thankfully, and have encompassed other species that are close to us.
But I do think that we will always draw a line, especially when it comes to pigs and cows, animals that we cultivated, essentially invented (or at least manipulated) for our own needs. Is it arbitrary? Probably. Cruel? Maybe. But I think it does, weirdly, keep us closer to the animal kingdom, in which webs of sympathy are far, far smaller. That might be rationalization for keeping up something- the eating of meat- that I have a vague feeling is wrong, a feeling I am unwilling to chase down, because I love it too much and know that I will never give it up.