Here's a meme that attempts to express an argument from a forthcoming philosophy article (author and title forthcoming). I don't suppose articles are summed up as memes very often! The abstract of the paper is below the fold.
Meanwhile, many ordinary pro-life people think that stopping abortion is far and away the most morally urgent socio-political issue. They reason that since abortion (in their view) consists in the unjust killing of so many human persons, fighting it should be an overwhelming priority.
Here I argue that this way of reasoning about the urgency of combating abortion conflicts with the usual response to the Embryo Rescue Case. If the fact that you should save a developed human rather than many more embryos doesn’t imply that embryos lack personhood, then embryonic personhood doesn’t imply that you should save embryos rather than many fewer developed humans.