General reply to TH, since earlier comments were deleted:
If you want to make the self-defense argument, then show me another case, other than that involving an unborn child, in which I can claim self defense because the person in question was simply existing/hanging out (read, not doing anything), and the circumstances surrounding that put me in serious apprehension of my life.
I'm not making the claim that, legally, malevolent intent is or should be necessary on the part of the person against whom I am defending myself. But some form of action, some kind of activity, on the part of the person against whom he defends himself, seems a sine qua non for any person reasonably to claim self defense.
Show me an analogous case, TH, in which the person against whom I defend myself does absolutely nothing, and yet I am still justified in intending to kill him. [Morally speaking, St. Thomas Aquinas and St. Augustine seem to say that only a public official can intend to kill anyone; private citizens cannot directly intend to kill, even in self defense.]
Conversely: if you insist on this line of reasoning, you must admit that any pregnant woman whatsoever, so long as she doesn't want the baby in her tummy, can act in self defense by means of abortion. Her bodily integrity, etc. is impaired by the very presence of the unborn child. Or, if you refuse to admit this, you at least must admit it for all victims of rape.