Why would people be against abortion?

Why do you think it is my position that needs to be justified, and not the opposing position? "Equal unless there's a reason not to be equal" is the default position in every other situation, so why wouldn't it be here?

Would you be prepared to use this same line of reasoning in other situations? For example, when white colonialists made it legal to hunt and kill the African bushman on the basis that they were "part of the flora and fauna" and as such didn't qualify as human life? Would it have been valid for the colonialists to say "I've yet to see an iron clad reason why their lives should be of equal value to ours?"

Because I want to understand what the "iron clad" reasoning for your position is. 'Why wouldn't it be this way?' doesn't come across as "iron clad". You are assigning absolute answers to problems that have been debated and discussed for hundreds of years, e.g. topics like 'when does life begin?', 'what makes something alive?', etc.

I am trying to understand what your reasoning is. I'm not presenting my own argument for why abortion should or should not be allowed, you are.

I am not the one who needs to provide iron-clad justification. The burden of justification is with those who argue for inequality and exceptions. My position is for consistency, simply because it's the default. And the reason it's the default is because if it wasn't, there'd be nothing to stop us from selecting any group of people we don't like and saying “well who says they’re really human and that their lives are as valuable as ours?” and then start killing them.

I'm not tied to my position though; I'm happy to move from it if someone does provide an iron-clad justification as to why their lives are less valuable. But I haven't seen anyone do that.

You do need to provide a justification. You have asserted that embryos and fetuses qualify as human life without giving a reason, not even a definition of what "human life" means.

How we define "human life" can have wildly different implications on how we view protection and care for everything under that category.

Never understood why people are against abortion especially when it comes to strangers online. It doesnt affect you so why are you bothered about it. People will always make excuses like "dont have sex" or "its killing the baby" but i dont understand why some people act like a POTENTIAL life is more valuable than the mother - who is currently living a life.
People will always say stupid **** like "abortion is only okay if the girl got raped" but honestly i think thats just a stupid statement because a girl should be able to get an abortion because its her body? They have the right to control their bodies and its just annoying to see posts on social media with people spouting nonsense.
Only saying this because my friend thought she was pregnant and she was talking to her family that she will get an abortion. She's not pregnant but her whole family was against the idea but she was dead set on it. Again, why do people car, surely its better to support them? Abortion isnt exactly a walk in the park either.

If adults, teenagers, toddlers and infants all qualify as human life, then by extension fetuses and embryos do as well; they're just different points on the same spectrum. Unless you have a reason for creating a cut-off point.

I think some people gloss over a big part of the whole 'is this a human life?' argument by overlooking that if someone has got the idea into their head that a foetus is a human life, then there is prob v little you could say to change their mind again, no matter how much you talk about cells, wombs, trimesters etc

I don't share such views, I can just kinda see how someone who does would be appalled at mine and feel it was genuinely wrong to treat a foetus as some way disposable.

Why should they be considered human life just because they are on the same spectrum? And of what "spectrum", exactly? How is this spectrum defined? Why is human life that is not on this spectrum excluded?

I'm not sure what part of this you don't understand. Adults, teenagers, toddlers, infants, fetuses and embryos are all just different stages of every person's life. The "spectrum" refers to all points from the start of their life until the end.

But how is that "spectrum" defined? What are the start and end points? Why are points outside that spectrum excluded, why are they not considered human life?

It sounds circular, 'Embryos are human life as they are part of the spectrum of life'. Be explicit in what these terms mean.

I don't understand what you mean by "points outside that spectrum". What points are you referring to?
The spectrum includes all points at which the individual (a) exists and (b) hasn't died yet.

I don't know what the points could be because you haven't even defined what the start and end points of the spectrum are. 'Life starts when it starts, line ends when it ends' is all you have said.

I defined it in my earlier post. Any point at which the individual exists and has not died yet.
I think we all know what "existence" means? I think we all know what "dying" means?

I don't really see the purpose of this discussion. If I said that a six year old child is a "human life" we wouldn't be asking "Ah well when are we exactly defining life to start and end? Has it really started yet or does it start at age 7?" It's already clear enough what these terms mean.

You still aren't being explicit. "Individual", "exist", "human life" are extremely vague terms in this context since different people can have different views on when and where these things occur.

Does human life only start to exist at fertilisation or after a certain number of weeks of pregnancy? Or does it begin prior to fertilisation, does an unfertlised egg qualify at human life? Or does it only begin once something has been born?

Clearly we don't all agree on these terms, that's why the question has been raised. I don't see how you can expect other people to give you "iron clad" justifications for their views if you can only dance around your own.

No, an unfertilised egg wouldn't qualify as human life because it's not part of the spectrum I outlined earlier. It doesn't develop into a foetus, infant, toddler, adult etc. over time. It only has half the genes of a human.

I've already been clear enough. The idea that the terms I've used are "too vague" would mean that one could just as easily say a 6 year old child isn't a "human life" either. We all already know what terms like "individual" and "exist" mean without needing to get metaphysical about it.

And why should we use that spectrum to decide what does does not qualify as human life? In other words, why should we not view it as human life just because it doesn't develop into a fetus over time (which itself is a nebulous concept)?

I have said it before and I will say it again, we clearly do not all agree on what terms like "individual" and "exist" mean. Some people would disagree that something which hasn't been born would qualify as an "individual", for example. You see comments in these debates like 'just a couple of cells' for exactly this reason, a lot of people do not consider embyros and fetuses as "human life". The whole concept of personhood has been debated for centuries. If you have found an iron clad solution to the problem then I would like to hear it.

For exactly the same reasons why we wouldn't consider a cat or a banana "human life". They don't contain a set of human genes, and they're not part of the spectrum containing everything else that we consider to be human.

People disagree about what constitutes "human life" because they are drawing arbitrary (IMO) cut-off points in the stages of development before they choose to call it "human life". It's not because a sentence like "this fetus exists and it has not died yet" is difficult to understand. No doctor on a maternity ward is going "ah but does this fetus really exist though? What does existence even mean?" Those are just irrelevant, semantic games to try and blur the issue. If they were valid, then one could just as easily be used to argue that a 6 year old child isn't "human life" either.

What makes their cutoff points arbitrary but not yours?

'Does not contain human genes' is an arbitrary cutoff.

'Does not develop into a fetus over time' is an arbitrary cutoff.

You have chosen to define something as "human life" after a certain cutoff, others have done the same just with a different cutoff. What is your iron clad justification for the cutoffs you have used?