Yes, those images are from fiction, but the concept is not an alien one. And we've already discussed how at least one New York politician advocated for post-birth abortions.
Also there's this little gem from an article written by a couple of "bioethicists":
“We claim that killing a newborn could be ethically permissible in all the circumstances where abortion would be. Such circumstances include cases where the newborn has the potential to have an (at least) acceptable life, but the well-being of the family is at risk. We propose to call this practice ‘after-birth abortion,’ rather than ‘infanticide,’ to emphasise that the moral status of the individual killed is comparable with that of a fetus (on which ‘abortions’ in the traditional sense are performed) rather than to that of a child.”
You yourself have based your arguments not only on the purely legal idea of "the law says it's not murder, so it's not murder" (an argument WWII Nazis may even have made regarding the Jews), but also on the presumption that a fetus has "no personhood". Well, by your definition, babies /after/ birth have no personhood either, not for the first 1-2 years. So no problem aborting them either, amirite?
From the same article:
“The moral status of an infant is equivalent to that of a fetus in the sense that both lack those properties that justify the attribution of a right to life to an individual.”
So by your own reasoning for why you support abortions, you should be just as supportive of /post/-natal abortions.