This boils down to a fundamental difference of view of women and reproduction I think.
Those who believe that life begins at conception and believe that any act to damage / remove / etc after that point is murder, same as killing a an adult.
Those who believe that a woman is an important being in her own right and should have sovereignty over her own body full stop, and see an embryo / foetus as a potential life, but not one that outweighs the life of the woman, given that it is dependent on her body to survive, it is a part of her body.
Most people do lie somewhere in the middle in most of the UK, believing in a woman's right to choose, but with certain constraints. There are perpetual arguments around moving the cut-off, and about the situations where abortion can be carried out to term, and the 2 doctors thing, but still, we we have the NHS, it is legal, and obtainable, and something like 90% of abortions are carried out before 13 weeks.
This is the middle ground I think.
For the anti-abortionist people, when you look at groups, societies where it is illegal, and where the population are generally against it, religion is usually involved, and abortion is under attack along with a host of other things that affect women. And they are winning. It is push push push. In the USA, it is the fundamentalist christians, they are using any means at their disposal to shut it down. There is direct collateral damage around maternal mortality - but this is OK - because the end justifies the means - even if the means result in mothers dying and babies being left without a mother. Which is pretty peverse IMO.
I don't believe that you can decouple the views of these groups, from the generally toxic view of women outside of this issue.
SPUC are extreme. They believe in no abortion under any circumstances. They are the group under discussion here as they are the group that produced the leaflets the OP started the thread about.