The common pro-life argument against abortion is that the killing of an innocent person is always murder, and that all fetuses are innocent people; therefore, all abortions are murder…but who’s to say that either premise is correct? I’m willing to accept the latter, but I question the former. I think I can give a few examples of when killing innocent people is not murder.
A car accident: somebody jumps out in front of your vehicle and you hit them.
Collateral damage in a war: in 1990 coalition forces accidently bombed a bunker full of civilians. I believe they killed 2,000 people in this single raid and that many were women and children, but we don’t call THAT murder.
I could go on. So, I ask: Is it always murder to kill an innocent person?
First, let's dispatch with the abortion argument you mentioned. This is a classic example of a 'begging the question' argument. (So classic it appears in tons of logic texts!) The reason why it is question-begging is because whether or not a fetus is a person is exactly what is under debate in the abortion controversy. By assuming the very point they are looking to prove, proponents of this argument commit the sin of begging the question. Your problem is a bit different, and more interesting. You are wondering if the seemingly attractive premise "killing innocent people is always murder, and therefore is always wrong" is actually worth much. All of your examples seem to be cases of killing innocents by accident. (Whether war is ever an accident is a question we can [sigh] leave aside.) I think it is reasonable to say that killing someone by accident is not murder, though it may be grossly negligent and blame-worthy. You want to define murder as killing another, with the malicious intention...