[fastball]

The problem is that, as far as we can tell, they're not self-aware. They have no concept of "captivity". Their life is their life; they don't have hopes, dreams, or desires. They eat, shit, and fuck. That's all they do in the wild, that's all they do in captivity.

The beauty of being human is that we are not controlled by our instincts. We have meta-cognition, which therefore makes us distinct from all other animals. This is why the vast majority of the earth's population agrees that killing a human and killing an animal are very different things.