Forcubly removing an unwanted trespasser from your property is not, by definition, "aggression." The only valid argument against abortion would be that voluntarily creating a baby creates a moral obligation. If you can prove that there is such, I'm all ears.
First if all, if a helpless little baby were placed on your property against your wishes, you would not have a legal or moral right to crush, decapitate, poison, or dismember that child.
You could call Child Protective Services or 911 and ask public authorities to take this child alive and safe off of your property as soon as it can be done without risk to the child. Bashing the kid with a shovel would be a criminal act.
Trespassing is not a capital crime. Moreover, the child, passive and helpless, was placed there. He did not intentionally or recklessly PUT himself there. He did not aggress.
So killing s child is still murder, even if the child was begotten by rape.
If intercourse was consensual, an additional argument of an “obligation to care” can be made, since all persons of reproductive age realize that intercourse can lead to pregnancy. This calls for strict liability.
Do you accept that there exists such a thing as parental obligation?