Well, actually, the entire opposition to abortion is based on the notion that fetuses are as human as infants - a position that has just as much, if not more, basis in reality as the opposite.
Yes, I know, but my point was that the sentiment that they are is practically a religious one - not that it is tied toward any particular religion, but that it is considered a dogma that is taken for granted. Probably a better example would be the "life begins at conception" thing, which some sects, like Southern Baptism, indeed made it a doctrine of their faith, as opposed to one granted in empirical reality. Thus, for the most part, it is as pointless to argue about as saying "GOD EXISTS NO HE DOESN'T"
In conclusion, the only proper response to abortion posts are dead baby jokes.