But there's nothing that says that boundary has to be birth. It would depend on when you think a person exists. Some people would say that happens at conception. Others would say it doesn't happen until well after birth (indeed some philosophers have said it doesn't fully happen until adulthood).
Is evolving into something with purpose also a purpose? Then unfertilized eggs have a purpose - to become fertilized - and if you aren't making that happen nonstop it's as bad as killing someone.
The article says every person has a purpose. As I said before, people's opinions might differ on exactly when a person exists during the human developmental process, but as far as I know nobody has ever argued that unfertilized eggs are persons.
(Note that unfertilized eggs do not "evolve into" humans--only fertilized eggs do. So even on its own terms your argument is not valid.)
But there's nothing that says that boundary has to be birth. It would depend on when you think a person exists. Some people would say that happens at conception. Others would say it doesn't happen until well after birth (indeed some philosophers have said it doesn't fully happen until adulthood).