Because if you sent a zygote into space and it was recovered by an extraterrestrial, they would view it as a lifeform and they would give it some appropriate name. It's not a sandwich, it's not a plant, it's not a disease. If we found a similar lifeform on Mars we wouldn't say it's some random bullshit, either.
This is exactly what scientists do when they discover a new species of plant or bacteria. Recognizing that something is a lifeform, giving it a name, and studying it, does not mean that what is being studied is a sentient being, and the concept of personhood only applies to sentient beings.
Also to say a fetus is not a human being is insane, it literally looks exactly like a living humanoid. Medical professionals call it a fetus until the moment it is born, it is preposterous to say that a baby 5 minutes before being born isn't a human.
It doesn't look "exactly like a living humanoid" until well within the third trimester, and for the first few weeks, it isn't even possible to distinguish a human embryo from the embryo of any other cordate species without a DNA test. The period of fetal development where personhood could arguably be a matter of contention is far later than the window when the vast majority of abortions are performed, so it really isn't constructive to your argument to quibble over this.
Yeah, because it's unique. Saying that it doesn't remind you of anything else in life doesn't really mean anything.
Except it's not unique. One could quite easily apply the logic pro-lifers use to situations outside of abortion, and arrive at conclusions that just about all of them (I hope) would find immoral.
There are plenty of people who have two functioning kidneys; there are even a handful of people who are born with three kidneys. Would it be moral to demand that these people give up some of their spare kidneys so that someone else can live? Or is the right to bodily integrity not something which someone else can infringe upon, even if it means them dying?
And yet their arguments were so sound that the Declaration was used against them decades and centuries later to argue against slavery as a moral evil and for civil rights of the unlanded classes, blacks, and women. The words outlived and outshone the writers, and all of them would agree and hope for that.
And yet it remains the case that this evolution in our understanding of rights hasn't resulted in the conclusions that pro-lifers have come to. In fact, it's done the opposite, culminating in Roe v. Wade. The legal and moral precedents which our society have set have invariably came to the conclusion that one person's right to life doesn't grant them the license to infringe upon another person's right to bodily integrity, and this is beginning from the very shaky assumption that a fetus is even a person to begin with.
Yes it is. My liver is a person. That person is me. If you point at my liver, you're pointing at me. Parts of me are me.
If you point at a fetus, you are pointing at a person, and that person is not the mother.
A liver can belong to a person, but it is not a person in it's own right. Someone who has suffered brain death can still have a working liver, but most people would not object to shutting off the life support system and killing it, because the person it used to belong to no longer exists. Keeping it alive also imposes a cost on other people by potentially denying them a hospital bed they might need, just as an unwanted pregnancy imposes a cost upon the woman carrying it.
Children have a right to the nurturing of their parents. All rights exist in a state of nature, before The State is even formed. All rights exist without the state. You do not have a right to a state, or to any of its services.
I was a libertarian too once; then I turned 17.
Why is the alternative of not abusing your child not an option? Again, why do you just write off all actually good options and then decide which of the bad options is least bad?
I never said it wasn't an option. It should go without saying that people shouldn't abuse their children, just as it should go without saying that people should take steps to avoid unwanted pregnancy, but in the real world, morality can't always be proactive. Ultimately, people are going to make mistakes; people are going to do bad things, and when that happens, society has to decide how to best respond to the situation. You can't just let abuse go unpunished, just as you can't make unwanted pregnancies magically disappear. I don't pretend that either scenario is ideal.
Spiritually and genetically there is actually a strong case that they are the same person, but that's a whole argument
There is absolutely no sane case that could be made for such a notion. If one identical twin commits a crime, do you suppose that they should both be prosecuted? Don't be silly.