Not too long ago I had a long conversation with an elder and at some point the topic went towards exceptions to the rule and how everything is not black and white.
His example he gave me....he asked if two married sisters who have unbelieving spouses were invited to a christmas party at their spouses workplace, if it would be wrong for both of them to go. He went on that it depends on the reasons. He said sister A husband is well mannered and responsible, is okay with her not going, and her going there would merely be participating in everything. There is no harm in her not going, so as an elder he would tell her she isn't allowed to go. But sister B's spouse many times may drink too much, etc, and their marriage is strained, he is insisting she go, so 'out of love', for her the right decision is to go. She'll be there but not be saying merry christmas, etc.
His whole point though is that when things are questionable, that love trumps all. He also went on to say that if a brother had a job and suddenly they were making war devices, if he should leave his job right away? He said no, he has a responsibility to provide for his family, so he must first secure employment elsewhere. If they saw he wasn't trying to leave and was taking too long, then he'd be in trouble.
Now I wish I thought of this at the time, but if he was talking to me as someone taught by the organization, then it recently dawned on me that the same SHOULD apply to the blood issue with them. The mother of a family with small children needs a blood transfusion, even though they believe they technically can't take it, since the love and taking care of the family issue trumps all, then in that case she must take it because if she dies, her children will be uncared for, her husband couldn't do it alone.
Then take it a step even further, Jesus showed that anything out of love there is no law against and no sin. Eating blood as a meal when one can eat many other things is quite different from needing blood to save a life. They didn't have blood transfusions back in bible times. So the law of love would mean that a blood transfusion, to save a life, would trump abstaining from blood.
Just like healing on the sabbath or saving a life trumps not doing any work.
I wish I thought of that when I spoke with him, I wonder what his response would have been.