Temple Grandin's rationale for eating animals

On Valentine's Day, I withheld judgment on "Temple Grandin's dilemma," pending further information.
    Further information I now have, from her wonderful book (a must read for anyone interested in other animals and our relationship with them), Animals in Translation: Using the Mysteries of Autism to Decode Animal Behavior:

If I had my druthers humans would have evolved to be plant eaters, so we wouldn't have to kill other animals for food. But we didn't, and I don't see the human race converting to vegetarianism anytime soon. I've tried to eat vegetarian myself, and I haven't been able to manage it physically. I get the same feeling you get with hypoglycemia; I get dizzy and light-headed, and I can't think straight. My mother is exactly the same way, and a lot of people with processing problems have told me they have this reaction, too, so I've always wondered if there's a connection. If there's something different about your sensory processing, is there something different about your metabolism, too?
    There could be. It's possible that a brain difference could also involve a metabolic difference, because the same genes can do different things in different parts of the body. A gene that contributed to autism might contribute to a metabolic difference, or any other kind of difference. Parents have always said that their autistic children have lots of physical problems, too, usually involving the gut, and mainstream researchers haven't paid a lot of attention to this.
    So until someone proves otherwise I'm operating from the hypothesis that at least some people are genetically built so that they have to eat meat to function. Even if that's not so, the fact that humans evolved as both plant and meat eaters means that the vast majority of human beings are going to continue to eat both. Humans are animals, too, and we do what our animal natures tell us to do.
    That means we are going to continue to have feedlots and slaughterhouses, so the question is: what should a humane feedlot and slaughterhouse be like?
    Everyone concerned with animal welfare has the basic answer to that: the animal shouldn't suffer. He should feel as little pain as possible, and he should die as quickly as possible.

...But eliminating pain isn't enough. We have to think about animals' emotional lives, not just their physical lives. We're responsible for slaughterhouse animals; they wouldn't even exist if it weren't for us. So we have to do more than just take away physical pain.
    The single worst thing you can do to an animal emotionally is to make it feel afraid.... [pp. 179-80, 189]

So, what judgment am I now prepared to make?
    An observation or too first. In the first sentence quoted, Ms. Grandin says that because we evolved a certain way, we must eat animals. Clearly that is not so; many people are vegetarians.
    She also says that, because "humans are animals...we do what our animal natures tell us to do." Not entirely. Human animals are also moral animals; the aforementioned vegetarians have chosen not to eat meat, either because they think they ought not [morality as a set of principles for avoiding evil and doing good) or because they judge that avoiding meat affords a better (because healthier) life [morality as a set of principles for attaining the good life].
    That said, I still can't bring myself to judge Temple Grandin. Who would I be to judge someone who has done far more for animals than I could ever hope to do?

A subtler, perhaps deeper read when it comes to the morality of eating animals seems to be on offer in Jonathan Safran Foer's 2009 book, uneuphemistically titled Eating Animals, which I've just begun to read, along with entering freshmen at Duke University and the University of North Carolina at Chapel Hill. It's their assigned reading for book discussion their first week on campus this fall.