It's a collection of cells. At what point does a collection of cells become a human? I think personally its when they develop a brain.

Things you think personally are not important when it is about church not just you. Catholic Church current consensus is human is human after impregnation. Of course there were times when catholic theology has some different view about the exact moment,but we the subject we discuss is catholics suggesting Joe Bidet because of his support for abortions shall be excomunicated. And according to church law - shall be as it is enough to do so, there is no need to wait for proving he is pedophile and satanist practising child sacrifices - such attitude about abortion is enough to excommunicate him.