I’m aware that a fetus is human. That has never been up for debate. And I agree that treatment shouldn’t be based on intellect or mental capacity. That is also not up for debate. What it comes down to is bodily autonomy. When a fetus is reliant on the body of another, the person hosting that fetus as a right to veto that use. Just like a person needing a blood transfusion couldn’t require you to donate blood just because you were a type match. If the pregnant person doesn’t consent to the pregnancy, they can receive a medical procedure to terminate that pregnancy. Bodily autonomy means your body belongs to you alone and you AND YOU ALONE have the right to control who uses it and when. Opening it up to government restriction and control basically turns it into a system in which mostly cis men are controlling the reproductive rights of mostly cis women, and that’s a horrific and terrifying thing.
Such an excellent point though! We wouldn’t dream of mandating the donation of a blood transfusion regardless of whether or not a person’s life is a stake. It’s uncomfortable ethical territory to be in, but legally we always grant that a person has the right to refuse compromising their bodily integrity even if it means the death of another sentient human being.