Why is "up to the point of viability" the finishing line and indeed what exactly is "viability." Humans aren't born fully formed and functioning. Should a mother choose not to feed a kid it dies. I guess you could make the argument that we aren't viable until we can actually go out and secure food and shelter for ourselves.

Eliminate "viability" and I think this argument was put forth more succinctly as "I brought you into this world and I can take you out"