There are several concepts at play here that are important to distinguish.
The point at which life begins:
- spiritually
- ethically
- legally
Item 1 is a religious issue. Let’s agree not to discuss it, because we won’t convince anyone of anything.
Ideally, 2 and 3 would be as close as possible. However, religious people would very reasonably say that for them, 1 and 2 are the same. Again, to avoid the religious argument, and try to come up with an ethical one from a humanistic standpoint.
Legally, it is what it is, which varies from state to state. But the OP’s argument was essentially an attempt at a humanistic argument, without recourse to religious beliefs. Which brings us back to item 2.
There’s a good deal of general agreement that human life is of high value. We all tend to agree with that because, well, we’re humans, and what goes around comes around. The argument against child abuse stems from this assumption. No argument there.
So the question becomes, when does human life begin? As mentioned above, this issue is fraught with difficulty. In some cultures, it was acceptible to leave an infant to the elements as a form of family size control – better than having the whole family starve due to another mouth to feed. That seems heinous to the modern mind, but has a pretty simple utilitarian argument.
Birth would be a convenient point, but most of us agree that’s too late.
Before conception doesn’t seem sensible, since at that point everything is hypothetical. (The same people who criticize abortion by pointing to an out-of-wedlock child who is now loved, would not endorse the act that created that child. BTW, that child is me, and also my son, but that’s another story.)
So, we have to pick some point between the two. My point (which echoes similar points above) is that Nature does not dictate this decision. Remember that the sanctity of human life is based on a general agreement. That agreement depends on an agreement of what human life is, which includes where it begins. If we set that point at the mythical “point of conception”, we lose a lot of the crowd of people who originally agreed with us that human life is sacred. They don’t think that the sanctity of human life begins at conception. So we’re back to square one.
Most states currently choose some point between the two extremes of conception and birth. That’s what I would choose, and I don’t want others forcing their religious beliefs on me. They are free to refrain from abortion.