The Bible really has nothing to do with it. I posit that the Bible has become little more than a prop for this religion.
This is a very good point, allow me to post an excerpt from a recent email with an elder:
The information that Jehovah provided to the bible writers is 100% perfect thought. Does it lose perfection when it is transferred from the inspired mind of the bible writer to the paper? We don't know for sure but maybe. Does it lose more perfection in the next step from the original paper to the scribe? Absolutely! If it didn't there wouldn't be a need for all the adjustments in thinking as time goes on. The point is we can't be 100% sure that we have everything that's written today exactly right. So where does that leave us? It leaves us in the exact same position that the first century Christians found themselves. Determining exactly who the agency is that Jehovah is working through to get the truth or proper direction from. It obviously wasn't the religious leaders of that day. Although they just knew in their own minds that they had it right. They were so confident in their thinking that they even argued with Jesus, and missed identifying the true agency.
This is the kind of people you're contending with. As you can see, this elder believes, and thus witnesses are supposed to believe, that the bible is SECOND in authority. Rather than trust it they trust the organizations interpretation of it - clearly what he said above. So the organization says blood transfusions are wrong, then they are wrong- regardless of what you can say about the bible, you aren't gods chosen organization.