I am a pro-life atheist

[Abracadabra]

Step 3.5: The end of life is defined with brain death. Why should its start not be defined the same way?
Step 4: Since there is no credible evidence of any fetal cortical activity before about 150 days, it makes sense to say that human life truly begins around that time.

Those are extremely good points right there.

A single fertilized cell would certainly be "brain dead".

So to define human life at conception has no rational basis at all.

I'm 100% in agreement with you on that one.

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In my view, that is tantamount to murder.

If you're attempting to argue that to abort a few cells at conception equates to murder, I think you're going to have a lot of opposition to that.

That's an extremist view that really has no justification at all, IMHO.

I would certainly fight that tooth and nail myself just on principles of humanity.

For you to demand that all unwanted babies must be taken to term. Is the same as demanding that unwanted humans must be brought into a world where they are not wanted even by their own parents!

I would question the morality of that very thing myself.