Abortion is murder. That "non human bunch of cells" is genetically human since the second the sperm cell merges with the egg. They are clearly marked as a human being from the biologic side. Being human is not about having a functioning brain. Animals have functioning brains, but are they human? Some species of monkeys are self aware, does that mean they are human?. It is also genetically different from the mother, so anyone saying it is part of her body is ignoring biologic and scientific facts. This means it is murder, as the baby is clearly human from the moment it exists. Saying we should be allowed to murder non born babies because it is dependant of the mother is opening the topic to a lot of abuse. Should we also be allowed to kill minors, because they are dependent of their parents? How about killing non working women who depend on their husbands? And what about blind people? They are pretty dependent too. How about poor people who depend on the state to get food and clothes? Hey, I have an idea. Let's kill every non self reliant person in the world, including employees, as they depend on their boss economically. Let's kill all presidents, as they depend on voters to get there.
But that's a fallacy unto itself. 'Murder', first of all, is 'the illegal killing of another person'. As abortion is legal, it isn't murder. Also, a fetus does not possess the qualities necessary for person-hood until at least the 26 week point in pregnancy. That is, a subjective mind and consciousness, and self-awareness. A functioning higher brain, in the real world, is required to have any of those qualities. As a human fetus does not have a functioning higher brain until 26 weeks, defining it as a 'person' before that point is literally incorrect. Due to those two factors, equating abortion with murder is simply not correct. Therefore, abortion is not wrong. Also, what any given book has to say about any given topic has no bearing on the moral or ethical nature of that topic. The bible is no different.
The Bible says "Thou shall not murder". Christians treat abortion like it is a crime because abortion is murder, which is a crime. Murder is wrong. It' s really simple. Silence in the Bible does not necessarily mean contradiction. The Bible speaks against murder. Now if somewhere in the Bible it said the exact opposite then it would be a contradiction. Since the only command given on the topic of murder is that is wrong, than one should understand murder to be wrong. Again, Abortion is murder. Murder is wrong. Therefore, Abortion is wrong.