Doctors are beholden to the Hippocratic Oath, so it would be immortal for them to do harm to the one patient as opposed to healing them - even if the outcome of said harm is to the benefit of those needing transplantation. The Hippocratic Oath is the active agent dictating good vs. evil in this particular analogy, which is why donors of organs are required in the first place, as a donor waives the expectation and permits the action to be done without effective harm (as long as said donor is dead).