"Babies are...not fully human yet."
Can I quote you on that?
So a person with brain damage - or better yet, a hemispherical lobotomy - is half a human.
Tell me: if the brain is where the "humanity" resides, where does the brain come from?
Oh, yes... from the instructions of the original DNA. Which forms upon - you guessed it - fertilization.
How about you bring out some FACTS to base your argument on?