zehydra said:
What I'm saying is that morality against killing of others is only justifiable for humans. You could say that it's wrong to kill other animals as well, but it would be either arbitrary, or based on emotional attachment to animals.
I know that's what you're saying. I'm challenging you to establish why, and I think that you'd at the very least have to say that any sentient aliens deserve the same rights as humans. In other words, that species identity is irrelevant when it comes to determining if it's right or wrong to kill.
A different argument would be required to establish why killing non-sentient animals is wrong. One way is to simply ask if you'd kill a human with the intellect of a dog. If you said no, and also agreed to the condition above, then it should be just as wrong to kill a dog as that human.
But to answer your question, Life lives off of other life. We as living beings are required to kill in order to continue living. However, some people want to say that "killing sentient animals" is bad, or "killing animals" is bad, but I never see a real reason for it other than "they're like us".
So what if we're not really required to kill? It's medically very well established that humans can live off a vegetarian diet just as healthily as an omnivorous one (and at the very least, you could drink milk and eat eggs without killing). And why is "they're like us" a bad argument? What's different about the human that makes killing it more wrong than a sentient animal? If there is no real difference between the two, then doesn't it logically follow that it's just as wrong to kill one as the other?
Basically my view is that Killing is a necessary part of life, for consumption, and that deciding to deny other forms of life their rights to life over others because "they're like us" always felt way too arbitrary or emotionally-based for me.
In my view, it's deciding that humans are somehow more important that's arbitrary. Why on earth should my species matter when deciding my moral status? And my decision in this regard was motivated far more by logic and intellectual honesty than by emotions. I wouldn't eat a dog because I love dogs and the thought sickens me. I couldn't care less about pigs (who have comparable intelligence and sociability), but I don't eat pork, either.
(Note that I do think humans have qualities that make us more important than animals, morally speaking, though. They just don't have anything to do with what our species is.)