Because none of this has nothing to do with abortion.
It has to do with your rationalization of abortion.
You've been saying that it's justifiable for a woman to kill her unborn child
because the unborn child's body encroaches upon the mother's body.
If I've misunderstood you, please correct me.
In my dumb example, the baby's body encroaches upon my body as well. Yet... you say I would not be justified in killing the baby, and the baby's body has not, in fact, encroached upon my body if I had to "sneak up on the baby and knock him unconscious."
So, why does the "sneaking up" part preclude any bodily encroachment on the part of the baby, in the events that follow?