I heard a good analogy the other day.
If I jump out of a two story window for the fun of it I would be putting my life in danger I think most would agree. Now if the house was burning down and the only chance I had of survival was to jump out that window almost everyone would say I did it to save my life and would agree on that choice.
Now take that with blood. To just abuse blood for the fun of it I would agree that it is completely wrong. Now if your survival depended on blood, even if it may come with risks, it’d be worth doing to save your life. Somehow I think God (if he’s out there) would agree.