Another Slashdot post (quoted material is another poster to whom I'm replying):
Say there's going to be a huge tragedy and someone's family
is going to die. If you could chose whether your family dies or someone
other family dies, which would you choose?
There is a large difference between "If between my father and some
stranger, I can only save one, so I save my father", and "To save my
father, I'm going to kill a stranger." Everyone understands if I throw
the single life ring to my dad instead of some random guy (though I'd
try hard to save both); everyone also undertands that it would be
monsterous if I killed the stranger to get the new heart that my dad
(hypothetically) needed.
My father's life is more precious to me, sentimentally, than
that of a stranger, so if all else is equal and no one's rights are
being violated his claims have priority to me. But his life is not,
ethically, more precious than that of a stranger; I cannot make a good
argument that his life is more precious than J. Random Stranger, so I'm
going to kill J. Random Stranger to harvest that heart. We all
understand that to be a violation of J. Random Stranger's rights.
Similarly, we all understand that if a dog and a human are both drowning
and we can only save one, we save the human. (Usually. If it's Hitler
versus Lassie, I'm saving Lassie.) But this does not imply anything about
the ethics of harming the dog for the human's potential
benefit.