But that's not what the question is about.
The question is about agency of one's own body.
Why would it be okay to murder someone because their father was a rapist?
Murder is a very charged way of putting it especially when the issue often involves a microscopic entity. I did not murder when I used mouth wash this morning in case you were wondering.
A person impregnated by rape should be able to stop the developing embryo in early stages of development because the pregnancy was not the result of volitional intention of the woman and women own their own bodies. Big government need not intervene.
A biological process within someone's body is the domain of that individual. In the case of pregnancy genetic material and resources are taken. The most basic right to property is ownership a person's actual body.
Or, to put it in the context of your analogy:
Why would it be ok to stop removing one of the people from under the rubble to shoot dead the one you can't save, even if there is no immediate risk to their life?
It could possibly be more humane to swiftly remove life rather than delicately when prolonging or reducing the period of pain is within the range of possibility. I do agree when considering an abortions, it is moral to consider the pain of the fetus.
Yes. Because:
You can use that extra time to figure out a way to extract both of them without stopping to put a bullet through the brain of one of them while rescuing the other.
It is not an easy scenario because there are two fully developed human beings involved here with identities, histories, memories, and communities. A person would be expected to remain for a reasonable amount of time, but leaving that resulted in the other person's death would not be considered murder.