The "potential life" argument holds no water. A fetus is already alive, else we wouldn't be discussing the action which prematurely terminates it. You're not guaranteed to avoid being struck by lightning as I type this MrIndigo, yet it's still illegal to harm you, even if you're standing outside in a field during the middle of a thunderstorm.
A cancer is alive; in fact, it even has human DNA. It has internal biological processes that is generically referred to as life. But that's not what I was referring to when I said life-in-potentia; that refers to life in the sense of a lifetime of human experience etc. You're deliberately shifting what is referred to by 'life' in the context in which I used it.
The point I was actually making before you so elegantly straw-manned it is that the anti-abortion argument that "It has a potential human life, therefore it is entitled to see that potential fulfilled" falls apart because it can be extended to artificially created zygotes outside of a womb (which the vast majority of anti-abortionists do not consider equal to a baby or an in utero foetus/zygote) or, when dragged to logical extremes, any potential combination of sperm and egg.
Essentially, if you make the argument that a potential human life should be treated the same as the life of a human that has been born, you have to then acknowledge your choice of time-of-fertilisation as the starting point is as arbitrary as the standard first-breath used to define legal personhood at the moment, or actively justify why that's not the case.