Yep, as a disability justice person I sometimes encounter resistance to this principle from people who are concerned about abortion being used for ableist reasons.
"Do you really think a pregnant person should be able to abort a fetus just for having Down's Syndrome?" people ask. Or just for having some genetic markers for Autism?
And my answer to that, always, is I don't think a child should be forced to be born to a parent that does not want them. And I don't believe a parent should be forced to give birth to a child they are not prepared for and do not want.
Is it ableist for a pregnant person to not want a disabled child? Sure, but I find myself far less interested in the purity or impurity of the pregnant person's morals than I am in the fact that disabled people and their families are provided almost no resources in society and are excluded for nearly every area of public life. There are many reasons why a parent might not want to give birth to a disabled child, or feel unprepared to raise them, that go far beyond that parent's own personal prejudices. And even those prejudices are informed by economic, legal, and social structures that make it very difficult, expensive, and isolating to raise a disabled child.
Furthermore, I don't care if any person gets an abortion for the right or wrong reasons because I do not think there should be some outside body that decides what a legitimate reason for seeking an abortion is. Who is going to determine whether a pregnant person is seeking abortion for the "right" reasons? Will it be the government? Which government, state or local? Will it be a social worker? A doctor? An ethics board? I don't trust any institution to determine whether someone is seeking an abortion for the right reasons or not, and I don't think it would ever be possible to institute laws that would prevent "unjust" or "immoral" abortions alone. Even if it were possible to magically only prevent abortions among people with horrifically bigoted views, I would oppose it, because as OP said, I do not believe in forced birth.
It really is that simple. And the same principles apply to a panoply of political issues that are needlessly concerned with an individual person's mental state or motives. Who cares why one individual person is doing what they do. Look to the economic forces, the demands, the resources, the needs not being met, and you will see the logic behind people's behavior. There's no need to legislate away a person thinking the wrong thoughts.