"When a parliamentary or social majority decrees that it is legal, at least under certain conditions, to kill unborn human life, is it not really making a tyrannical decision with regard to the weakest and most defenseless of human beings?....While public authority can sometimes choose not to put a stop to something which were it prohibited would cause more serious harm, it can never presume to legitimize as a right of individuals even if they are the majority of the members of society an offense against other persons caused by the disregard of so fundamental a right as the right to life."