Abortion: Establishing personhood and rights

[Dread Not]

So for the past couple of days an evasive twit has been messaging me on the subject of abortion. His first message to me took issue with my attacking the pro-life movement for using arguments like "Imagine the amazing person who will not exist if you abort!" He stated that is a weak argument held by a minority of the movement (bullshit), and that he had better arguments to offer like that a human is a human being at all stages of development. This went back and forth with me trying to establish that while an embryo is made up of living human cells, something can not be a "being" if it doesn't have a brain. I illustrated this with several examples including a brain-dead patient whose body of living human cells is kept functioning with medical equipment. Scientifically he is dead. He continuously has tried to claim scientific knowledge, citing a human in all stages of development has different "scientific qualifications" for being alive that none of my examples possess. I challenged him several times to list these qualifications and provide specifics beyond "science says they're different" until finally I told him he would answer my challenge or I was done with his evasive ass. He responded thusly:

It's quite simple, living human cells as a part of a larger organism are only units that make up the eukaryote. Human beings (at even the cellular stage) are the organism entire, with its entire genetic compliment and natural capacity to employ that genetic compliment to achieve all the biological functions we associate with the human species.

I ask for help in dissecting this because I'll be moving shortly, and won't have internet access for a few days where I'm going, so I'd like to wrap up my evisceration of him as swiftly as possible. The response I've just quickly written up is as follows:

It's quite simple, living human cells as a part of a larger organism are only units that make up the eukaryote.

And the only part of said organism that matters in determining personhood is a functioning brain.

Human beings (at even the cellular stage) are the organism entire

If personhood is dependent on being a complete organism then a person ceases to be a person when he has a kidney, tonsils, or foreskin removed. You can remove arms, legs and any number of parts from a person and it doesn't diminish his personhood so long as the brain is intact.

with its entire genetic compliment

Irrelevant. Nearly every cell in the human body has a complete genome.

and natural capacity to employ that genetic compliment to achieve all the biological functions we associate with the human species.

Capacity? This is no different from the "some day it will be an individual with thoughts and feelings" argument you took issue with. You are attributing characteristics to something that will only possess said characteristics down the road. My "capacity" to join the police force doesn't change the fact that I am not a police officer, and will not be treated as a part of the force until I actually join it.

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Any advice, suggestions, criticisms or commentary would be greatly appreciated. Also, this guy is very confident that science supports his position, so if anyone knows of any resources to the contrary I would be happy to see them.

[Vehrec]

What the heck is 'natural capacity anyways? Are we basing this solely on it's ability to implant and successfully grow in a womb? 70% of all fertilized eggs fail the test in that case. Furthermore, why is biological function important here? The brain dead have questionable personhood-and how about Artificial intelligences? They aren't human, but are they people? If your definition does not allow for C-3PO to be a person, I think you're too limited.

Oh, and he's using Eukaryote improperly here. Protists are Eukaryotes. Plants are Eukaryotes. His first sentance remains nonsense upon repeated readings.

[Edi]

Do a forum search of my posts with abortion as a keyword. You'll find plenty of arguments laid out that basically destroy his bullshit right off the bat.