AnimalCruelty

Like Barbara Ehrenreich (whose review of David Livingstone Smith's Less Than Human: Why We Demean, Enslave and Exterminate Others (St. Martin’s Press, 2011) in the LABR I read with great interest), this doesn't really convince met:

Smith offers his own theory of human uniqueness: We are unique in our ability to “dehumanize” each other and this, the reader will be astonished to learn, is a testimony to our superior intelligence:

Thinking of others as subhumans requires sophisticated cognitive machinery. Minimally, it depends on the ability to deploy abstract concepts like “human” and “subhuman” — something that is well beyond the reach of even the cleverest nonhuman primates.
There’s no point in belaboring the irony in Smith’s assertion that our apparent failure to consistently recognize conspecifics arises, not from thick-headedness, but from our presumed intellectual gifts.

Would smarter chimpanzees be capable of “de-chimpizing” each other? The empirical roadblock Smith faces here is that chimps do in fact sometimes “de-chimpize” each other, or treat each other with what animal behaviorists have called “gratuitous cruelty,” as if the “enemy” chimp were a non-conspecific prey animal, such as a monkey. Smith wriggles out of this by warning against attributing “human-like mental states” to chimps:

Now, chimps are very smart, but they’re not that smart. There’s no reason to suppose that they’re able to reflect on their own intentions or that they can grasp sophisticated concepts like harm. So it looks like Jane Goodall was right. Chimps can’t be cruel.

So chimps may act mean but they aren’t smart enough to really be mean: a line of reasoning which, I am sorry to say, makes Smith look suspiciously kind.

'Cruel', here, I suppose means not only acting in a horrible way to another being, but knowing that one is doing so, or rather knowing that one might be acting nicely but has instead chosen to act horribly. In other words the problem, as you adequately put it, is choice. This in turn, it seems to me, opens a fundamentally religious, indeed Christian context to the way we think about animals.  Dodgy, surely.