You've alluded to in vitro conception and offered it as a proof that there is no individual human life at conception, going even further to use the specious phrase 'fertilized egg' in reference to terminating an early form of human life. Here are the facts from a scientific point of view.
The haploid gametes (sperm and ovum each having 23 chromosomes) unite and a single combination of the 23 each chromosomes are united to form a 46 chromosome unit. Within hours at most, the first cell division occurs (called mitosis).
That initial mitosis is the proof, to a scientist, that a new individual human life is in evidence. With first cell division, the 'fertilized egg' term is nonsensical since there is no longer an egg but an individual human life.
What weighs on the side of scientists accepting mitosis as evidence of a newly conceived individual human life? The goal they have set for that newly conceived life. The scientists won't seek to ustilize the newly conceived individual human life for harvesting of its body parts (stem cells, in the case of the earliest individuality) if the proof of successful conception is not in evidence. without the proof of individuality via mitosis, a scientist will not consider the effort successful.
Conception of individual human life does take place in a petri dish with in vitro fertilization, the foolishness ravings of Orrin Hatchling notwithstanding. Once fertilization has been accomplished, the oeprator watches for cell division as the proof of successful conception. Later, a cell mass is implanted in an effort to accomplish a pregnancy, to achieve life support for an already existing individual human life in its normal state of life for that age bracket.
If you're going to argue for modern cannibalism, have the decency to be honest, else you're no better than the liars of NARAL and the other organizations supporting licit hiring of a serial killer to off the preborn.
As to personhood, the law is becoming vague even in that area. Suffice it to say that legal personhood and common sense personhood are at odds, presently. If our nation doesn't soon bring these duplicities closer together, to protect nascent life from conception onward, the cannibalization of embryonic and fetal individual human life will continue and grow to heinous levels.
Nice way to try to avoid debate. Can't stand the heat so you have to get out of the kitchen?
I'll try one more time:
You said, "We recognise the 'right to life' of a potential person, imo, -- not that of a fertilized egg/embryo, still inseperable from the life of its mother."
I say: A "potential person" has a "right to life", but a "fertilized egg/embryo" doesn't? What is the difference between the two?