Mild updating of my original position due to this conversation:

I still don't have many moral qualms about allowing parents to kill children, but realize that actually legalizing it in our current society would lead to some unintended consequences, due to considerations such as the Schelling point, and killing infants as a gateway to further sociopathic behaviours.

Part of my difficulty is that some humans, such as infants, have less blicket than animals. If its ok to kill animals, then there's no reason to say it's not ok to kill blicket-less humans. Then I realize that even though it's legal to kill animals, it's still something I can't do for anything except certain bugs. Even spiders I let be, or take outside.

So maybe a wiser way to reconcile these would be to say that since infants have less blicket than animals, and we don't kill infants, that we also shouldn't kill animals. It's what I live by anyway, and seems to cause less disturbance than saying that since infants have less blicket than animals and we kill animals, that it's ok to kill infants.