Now, you can argue that an unborn child/fetus/whatever is not a being or not alive, and therefore not deprived, and that's fine.
No, you can't. From the moment of conception, a fetus is alive. That's not debatable, nor a matter of opinion; it's a scientific definition.
As I've said before in this thread, I draw the line conservatively at intelligent social interaction.
Yeah, a fetus at the moment of conception is technically living. But (as Myndfyre anticipated) a tree is also living, and we cut down trees all the time. The fact that it's living doesn't invalidate the idea of abortion.
The argument (introduced in Rule's post, and extended in my post) is that aborting a
pre-sentient fetus is morally analogous to a woman not giving birth to a child in her lifetime, because the potential for life in both cases is the same. Since it is fine for a woman to live her life without giving birth, it must be fine to abort a
pre-sentient fetus.
In other words, and in terms of moral value, we equate the single-celled fetus to the ovaries of a virgin woman. There is no reason to attach more moral value to the single-celled fetus.