Because it treats birth as a magical process which transforms someone from a lump of cells to a full human. That is illogical.
No it doesn't. We have to choose a time where someone gets all the rights of a member of society, and we have chosen that time to be when they exist entirely separately of any other person. That's perfectly logical.
Don't confuse things you don't like with things that are illogical.
Please do tell, what line separates a human from a non-human? You can say legally it's birth, but that's not a logical answer because there's nothing magical about the birth process that suddenly transforms you.
Already covered above. It's perfectly logical.
We keep murderers alive for decades at huge cost to society on the off chance they might be innocent.
How can we not extend the same protection to those we know are innocent?
That's really not the reason we keep murderers alive for decades, but regardless murderers are full people with all the rights of a citizen and fetuses and embryos are not.
I knew you could figure it out.
Now THIS is an illogical position to hold. Not only that, but I'm sure even you don't actually hold it. I believe it was mentioned earlier in this thread and I've said it before: you are in a fertility clinic that's on fire and you have to choose between saving a one day old baby or a tray with 1,000 embryos on it. You can't save both. If the baby and the embryos are both fully people your choice is clear, save the tray. No same person would actually do that, however, because we don't actually view them as the same.
Of all the arguments for when human life begins, saying it begins at conception is basically the least defensible.
Legal chaos how? And when it comes to choosing between life and legal chaos, I think it's clear which is more important.
It would make in vitro clinics scenes of mass murder, it would make it murder for a woman to terminate a life threatening pregnancy, etc, etc.
Simply put, when we contrast the rights of full people and the unborn, people win every time.