When a man steals to satisfy hunger, we may safely conclude that there is something wrong in society - so when a woman destroys the life of her unborn child, it is an evidence that either by education or circumstances she has been greatly wronged. No one wants an abortion as she wants an ice-cream cone or a Porsche. She wants an abortion as an animal, caught in a trap, wants to gnaw off its own leg.
Abortion is a tragic attempt to escape a desperate situation by an act of violence and self-loss.
That was the premise to slavery. You could not protest the existence or treatment of slaves on the plantation, because that was private and therefore outside of your right to be concerned. The unborn child is the most helpless form of humanity, even more in need of protection than the poor tenant farmer or the mental patient. That seems to be the modus operandi of a lot of these 'population' groups. Each person must be treated as an end in himself, not as a means to improve someone else's life.