Does it surprise you to know that entire civilizations have been unable to see this inherent injustice? People have sacrificed individuals to their gods (which is what abortion is), allowed individuals to die so the social group would be stronger, eaten people for food (although that was often ritual), etc. etc. If you think I am only talking about ancient cultures without the benefit of modern science, I will point to the holocaust, black slavery, (much of which is going on today in sub-Saharan Africa), and the many examples of ethnic clensing that the last century delivered.
In Hinduism there are people who will allow a child to starve to death before touching him because the child is of the untouchable caste. They don't know the logic you are talking about.
The sanctity of human life is a concept that comes from G-d. It is not uniquely Judeo-Christian, because all peoples are descended from Noah and so all have some knowledge of G-d. But not all have acknowledged these concepts and many have found very rational, logical reasons to support their beliefs.
The fact that your logic doesn't agree either means you are of an inherently superior intellect (not impossible but it wouldn't be my first guess) or that your reasoning is influenced by the culture in which you were raised. Or, as it was put to me in my H.S. moral theology class, your viewpoint determines your point of view.
Shalom.
Well, the holocaust occured in mid 20th century Germany, a Christian culture. The slavery which currently exists in Africa, let's take Sudan for an example, is committed mostly by Muslims. Islam is, of course, a religion that shares a common ancestry to that of Judaism and Christianity, with very similar moral teachings. Christian America, prior to the latter part of the 19th century, condoned and practiced slavery. The Roman Catholic Church conducted a mass extermination of defenseless fellow Christians (including women and children) in the Albigensian Crusade against the Cathars. And, of course, it's abuses in regard to the prosecution of the Inquisition are well known to all.
Christian cultures have been, in many ways, just as barbaric and and inhumane as the pagan cultures that preceded. Now, I am thoroughly glad to see that modern Christians respect life.