There is no way to truly know when to draw the line when deciding whether a fetus is a person or not, is it when the fetus shows brain development, brain waves, pain reception, etc? Initial low level brain waves begin within 7 weeks or so, but there is no way to prove that some form of proto-consciousness or karmic continuum has not already begun to take hold in the tiny rupa process before hand.
Because of the ethically precarious position this puts one in, if we want to be 100% sure that one will not break the precept, one will not perform an abortion or enjoin someone to do so. I think AB is wrong on this therefore. This is because our only option that ensures one will not break the precept is the no abortion option.
If one performs an abortion while being 100% percent sure that it is not killing, then one is being ignorant, because the issue is very ethically complex, and there is no agreement, even among secular and atheistic moral philosophers.
If one performs an abortion while one is not sure whether it is killing or not, then one is being irresponsible.
And course if you know it is killing then all the worse.
Ultimately, even if Brahm turns out to be right, he is still being careless, because he cannot be totally sure about this, and with such an ethically serious and weighty decision, one must always err on the side of caution.
Vayadhammā saṅkhārā appamādena sampādethā — All things decay and disappoint, it is through vigilance that you succeed — Mahāparinibbāna Sutta
Tārakā timiraṃ dīpo māyāvaśyāya budbudaḥ supinaṃ vidyud abhraṃ ca evaṃ draṣṭavya saṃskṛtam — A shooting star, a clouding of the sight, a lamp, An illusion, a drop of dew, a bubble, A dream, a lightning’s flash, a thunder cloud — This is the way one should see the conditioned — Vajracchedikā Prajñāpāramitā
I have seen all things that are done under the sun, and behold, all is vanity and a chase after wind — Ecclesiastes 1.14