Explain the rape/incest exception to being pro-life

[nclib]

The right to self-defense has always been understood to have been applicable even when the "attacker" is not morally culpable, as in the case of an unborn child.

I'm not pro-life, but an example of this is where someone drops a child off a high floor and the child is about to land on someone who gets out of the way, causing the child to be more seriously injured. This would be still be self-defense and the person who moved out of the way would not be charged with anything.