It's idiotic because it makes no logical sense. They have put tens, perhaps hundreds of thousands of lives at risk, forced people to make life or death choices - all on the basis of a doctrine they clearly don't believe in enough to stick to a fundamental interpretation. Their woolly, arbitrary policy, made up of an evolution of compromises, requires a team of enforcers to keep the R&F in line and medical practitioners hoodwinked into thinking it's a reasonable religious position.
The fact that people did catch illnesses through transfusion in the past makes no difference to the validity of the policy. They don't maintain the policy for sensible doctrinal reasons. They don't even maintain it in order to improve medical technology. They do it because they have put some much into it - not least the lives of thousands - they cannot back down without seriously undermining their own authority and risking opening the floodgates of litigation.