I have no trouble defending
@Sha'irullah claim. All it takes is basic science, a rational view of the real world, and fundamental modern ethics.
The science is very clear. When two haploid gametes merge to form a zygote a new human being comes into existence. S/he may well die before reaching the stage of development called birth, but there's no misunderstanding about the difference between a potential human being (a sperm and an ovum) and an actual human being.
The real world, at least in the first world, includes the knowledge of where babies come from. That's potentially fertile sex. Nobody is forced to do that generally, when they are it's called rape. It also includes a wide array of contraceptives, prenatal care, etc. It also includes a social safety net which includes adoption agencies. People who choose sex, but not any of the other available options, are choosing the situation. That's where the capital C Choice is being made. After that Choice is made, competent adults have some responsibility. Because everybody knows that fetal babies are not free floating parasites looking for a host to invade. They are put there by the parents, who could have Chosen differently.
This matters enormously because of the inherent worth of every individual human being. For nearly all of human history, humans divided themselves into categories. Most people weren't considered important to most other people, i.e. they weren't considered persons. Modern ethics are increasingly inclusive, we no longer tolerate casual destruction of people because of their race or socioeconomic class or gender or whatever. We extend personhood to more and more of our fellow human beings.
Unborn human beings are about the last classification of human beings that are considered disposable people. The issues involved are extremely complex and require nuanced responses, just passing legislation or something is far from a solution.
But I have no trouble at all defending the premise whatsoever.
Tom