He asserted without justification.

I am guessing that you are playing some semantic game with that statement. Something like it's a fetus, which would be true, but belonging to one category does not imply the lack of other categories. But let's assume that we all agree that the definition of "baby" includes the requirement of living outside it's mother. It doesn't change OP's argument any. It is still the brutal murder of a human, all we did is remove a word that invokes compassion for it. Is there a particular reason why it doesn't deserve that compassion?