Honestly, I think that one issue pro life voters are what they are because the issue is a bit of a philosophical gridlock, which lets them launder in a hundred other far less defensible opinions into their political behavior. I know a girl who claims to be a pro life voter, but then also happens to be a right-leaning on virtually every other issue, by complete chance. It's just easier to be that than to be an open republican in certain circles.

This is all to say that you aren't going to defeat the pro-life faction through philosophy, you destroy them by destroying the right wing as a whole.