Animals have incest too. I guess that makes it right doesn't it?

Morality is a human thing and doesn't apply to animals. I also don't think animals just arbitrarily kill members of their own species, but I could be wrong. Killing animals of another species for food or protection is something humans do too and we don't call it murder by the legal definition.

I would call the act of killing another person immoral. Why? Because it just isn't right. Nature tells me that.

if you believe humans are just animals, I suppose anything goes. But if you believe humans are different, then morality comes into play.

Natural? Perhaps. Moral? No. Morality is defined by society, not by animal behavior. Society deems murder wrong.

Yes, it's immoral. But asking "why?" IS legitimate, and it's not a slam-dunk question to answer. The short version is that in order to understand why it's immoral, you have to have a coherent "basis for morality" -- something which provides a way to tell right from wrong. There's different levels to morality. For a child, right and wrong are based in the rules laid down by authority figures. For an adolescent, abstract notions of right and wrong prevail, as they attempt to formulate a coherent philosophy of ethics. For adults, "parental care" tends to take over -- the practical interest in making things work around them, much as a mother will hover around children and try to keep them from hurting each other. But a truly adult basis for morality has to do deeper than any of those levels, and ground itself in a place that isn't subject to the complexities of philosophy, the absolutes of dualities, and the moods of the moment -- the deeper basis of morality has to go to the heart of what it means to be a human being. What is that heart? It's simple to say, but difficult to realize: all humans are connected to each other and the whole of life. Actually, it's even more subtle than that... all individuals ARE the whole, in an intricate way. There's an "inter-identity" going on: the child starving in Africa isn't separate from me, and vice versa. And recognizing that provides a basis for morality -- the person I want to shoot in anger is, in a way, part of myself. To see that is to be able to let go of the trigger. It's also the basis for more formal codifications of morality, such as laws and ethical principles.

i say it's only right if you run out of cheez-its and have no other options left

it depends on the situation. Out of cold blood is wrong(IE George Bush's war) if it is for survival, say food, or water, then it's for the fittest. People murder all the time, with disregard for morals, even the (seemingly)innocent christian church murders to try to convert others to their religion, or to gain power.