People should be allowed to make their own informed decisions. If people refuse blood or mutilate their bodies it is none of my business.
However when a religion mandates and coerces that course of action - I have a problem. Most rational people can make decisions, and adjust those decisions as situations develop. The Jehovah's Witness religion make the decision for people (no blood) without regard to the situation at hand, and allow for no change in the decision regardless of the information presented.