Abortion is justified because “The unborn human is not a person.” Thus, murder has not been committed. With that line of reasoning, would someone be inclined to ask for forgiveness? There is no guarantee that those involved in abortion will repent, which is a terrible risk we play with another person’s soul.
This is the essence of this argument, to me. For Catholics, the consequences of abortion amount to (more or less) murder; and there are real spiritual consequences for this kind of act, potentially even torment in Hell. From your perspective, if you allowed someone to do this, then you might to some degree feel you had blood on
your hands as well, by not intervening. This is perfectly understandable.
But for atheists, there’s a corollary, and it’s not baby hating. If you don’t believe that a person’s suffering will be rewarded with Heaven, and if you think the entirety of a person’s existence is only that which is carried out as a single human life, then things look very different. If you bring in a child with severe disabilities, or into a broken household, or into extreme poverty, then you are knowingly creating a human being who will suffer more than enjoy, in essence, bringing that person into a kind of Hell on Earth, when they could have been spared.
They will ask you the exact same question: Why are you selfishly following beliefs that make YOU feel good, at the cost of the avoidable deep suffering of a new little person? Do they not deserve to be spared?
It’s hard for Catholics to understand, perhaps, but many non-religious people think that NOT bringing a baby into very horrible circumstances is an act of mercy and compassion, because in some cases there’s no light apparent at the end of the tunnel.