I argued in another post at another time that there's a difference between moral objectivism and moral absolutism. Moral absolutism is the view that moral principles are absolute in the sense they allow no exceptions. If something is wrong, then it's wrong at all times, in all places, for all people, under all circumstances, with no exceptions. Moral objectivism is the view that there are moral principles that are true independently of our preferences and beliefs, but one can be a moral objectivist and still believe there are exception to moral principles.
I was just thinking about how the question of whether there are exceptions to moral rules really depends on the granularity of the moral principles we're talking about. With the exception of a-moral choices (if there be any), you could state a moral rule for every single circumstance a person could possibly be in. But a moral rule book that contained all those statements would be impossibly long. Out of convenience, we speak of morality more generally than that. Instead of saying, "If you are in such and such situation, here's what you should do," we say, "You should be kind to people." Then we apply those more general principles to specific circumstances. We say that in general we should be kind to people, and since Bob is a person, we should be kind to Bob. Or we say since helping Bob move his furniture would be a kind gesture, we should help him move his furniture.
But there are degrees of generalization vs. specificity, which is what I mean by "granularity." If you had a really fine-grained moral rule book, then you might have one rule for each choice it's possible to make (e.g. when Jim drops his wallet this afternoon, you pick it up and give it to him). If you had a really course-grained moral rule book, you might just have two rules (e.g. Love God, and Love your fellow man). What occured to me as I was thinking about this was that the finer the granularity of your rule-book, the fewer exceptions we should expect their to be. If it were as fine as possible, then there wouldn't be any exceptions at all. At the same time, the more course the ganularity of your moral rule book, the more exceptions we should expect their to be.
As long as the Bible is, it's nowhere near as long as it would have to be for it to be a maximally fine-grained rule book. Instead, the Bible expresses moral principles in a general way. Some moral principles are more general than others. But that also means we have to allow for the possibility that some of the moral principles have exceptions.
Jesus explicitly taught this. While it is wrong to work on the Sabbath, for example, that rule can be overridden by a greater good--the good of saving life or healing. Just as it's right for you to rescue your mule even if it falls in a well on the Sabbath day, so also is it right for Jesus to heal on the Sabbath day.
There have to be exceptions to moral principles since there are such things as moral dilemmas. In general, it's wrong to lie, but if you're faced with lying to save somebody's life, or telling the truth and ending a life, you are probably justified in lying under those circumstances.
The Bible explicity forbids eating or drinking blood both in the Old Testament and in the New Testament. Jehovah's Witnesses interpret this prohibition as meaning that we shouldn't ingest blood in any way. So not only should we not take it into our bodies through our mouths, but we shouldn't take it into our bodies via tranfusion either. Personally, I think this is reading into the scripture something that isn't there at all, but let's suppose they are right, at least in a general sense. Let's suppose that at least in general it's wrong to take blood into your body through a needle inserted in your veins.
Nevertheless, this strikes me as being exactly the sort of thing Jesus was talking about. If a blood transfusion can save a life, then the value of the human life should trump the command to abstain from blood. The Jehovah's Witness refusal to allow for an exception to the general rule about blood drives them to what strikes me as being an immoral position--to allow people to die in order to observe the command to abstain from blood consumption. If we have an obligation to preserve life, then at the very least, this creates a moral dilemma since there are circumstances under which you can either preserve life or abstain from blood, but you can't do both. Which do you choose? If a Jehovah's Witnesses chooses to abstain from blood, are they not violating the principle to preserve life?
I haven't talked to a Jehovah's Witness or read their literature in a long time, but they used to answer arguments like these by saying there are alternatives to blood transfusions. So they attempt to avoid the moral dilemma by claiming you don't have to make that choice after all. I'm no medical professional, but from what I understand, they were just believing a myth. There is no artificial blood substitute that's just as good as blood. If there were, there wouldn't be all these desperate blood drives all the time. Blood transfusions are sometimes necessary to save life.
But let's suppose I'm wrong. Even so, this answer is evasive because the question remains: If blood tranfusion was necessary to save the life of your loved one (a child or parent), and you had to make the decision on their behalf since they've been in an accident and can't make the decision themselves, what should you do? In that case, you have to decide whether it's better to save a life by violating the prohibition against blood consumption, or to observe the prohibition against blood consumption by allowing somebody to die who you could've saved.
The irony in all of this is that the reason the Old Tesatment gives for why it's wrong to consume blood is because it's the blood that makes things alive. Blood has value because it symbolically represents life itself, and life is valuable. Well, if life is so valuable that we have to even respect that which gives life--blood--then it is the height of irony and madness to forfeit life in order not to consume blood. It's like being a general who surrenders his country in order to save his country's flag.