Religion completely alters the equation, you know.
I'm sure that that's what this is about for a lot of pro-lifers, but I also suspect everyone in this topic is smart enough not to use that as an arguing point. ultimately you can't change the mind of someone who believes in God and lives by biblical standards. you can, however, point out how all their justifications are inconsistent and poor arguments, ultimately forcing them to either abandon their position or admit that they believe an embryo is a person because God said so.