It hinges on his definitions, yeah.
A short version of his line of thought is this:
"If a newborn and those up to a certain age are classed as being closer to an unborn child than a 'real person', then abortion laws should be more applicable to them than laws that apply to 'real persons'."
He then makes the argument as to why newborns are closer to unborn foetuses.
Assertn's proposition says much the same thing in a different flavour. Difference is, the use of the label "protein" suggests that the babies are comparable to substances, while the debate compares them to something more like animals. They're living, no doubt about that - but they don't deserve the same moral considerations as a person.
Note that I used person as opposed to human. It's debatable over what else (if anything) is required for something to be considered a person besides being a member of our species.