Given that abortion is the greatest atrocity committed by the human race since the crucifixion of the Son of God, it's not surprising that arguments in its defence are equally atrocious. One example of many is "how many children have you adopted?" It is argued that anyone who is not willing/not able to adopt a child should not be able to argue against abortion.
The first clue to the fact that this argument is illogical is the fact that it does not apply equally to all pro-life advocates. To quote my friend, when people ask her how many she has adopted, she laughs and says "three, how 'bout you bro?" Suddenly, boom goes that argument, all because it was used against the wrong person. Yet, truth is universal. A £10 note in my hand does not become a £2 coin in yours. Because truth is universal, arguments about truth should be equally powerful no matter who they're used against. Therefore, this argument is fallacious even before we consider the morality of it.
But when we do consider the morality of it, we see just how depraved it actually is. There are many situations to which it could be applied. Have you ever hidden a Jew from a Nazi? If not, how can you oppose the Holocaust? Have you ever taken in a refugee from Afghanistan? If not, how can you oppose the Holocaust? You can even apply the "how many kids have you adopted" argument to kids who have been put up for adoption. In our culture, we do not often intentionally kill children once they're out of the womb, and we even look back upon cultures that did with the contempt they deserve.
The fact is, there is a major difference between "you shouldn't be killing these children" and "I will adopt all of those children". That's not to say they're incompatible. Many pro-lifers have adopted, or would adopt, a possible victim of abortion. I've even seen some stand outside abortion clinics holding signs saying "I will adopt your baby". But even those who are unable, or even unwilling, to adopt a child, are entirely consistent to say it's wrong to kill that child.
At the end of the day, the morality of abortion depends on two questions: Is it a human life, and is all human life equally valuable? For depraved reprobates, such as Planned Parenthood founder Margaret Sanger, the answer was "...we want to exterminate the Negro population..."(1), so clearly she disagrees with at least one of those premises. But according to science, from the moment of conception, human life is human life, and according to scripture, all human life is equal, and to take it unjustly is sin. Therefore, regardless of how many children each of us adopts, each of us must stand against abortion as the abominable act of mass murder it is.
References
1. Letter from Margaret Sanger to Dr. C.J. Gamble, December 10th, 1939