I would like to examine this premise. Jefferywhat is probably right that more people have died as a result of contaminated blood than have died due to refusing a blood transfusion. That does not justify avoiding transfusion on health grounds.
A very small proportion of people who need transfusions refuse them (assuming that JWs are the majority of these, and that JWs are not more prone to accidents and illness than the general population, it would be about 0.1% of patients), some die, and some survive. A small proportion of people who have received blood transfusions have received contaminated blood products leading to their death. Had all the people who received blood transfusions refused a transfusion - would more people or fewer people have died? The apologist can only answer that it is impossible to predict how many would have lived or died, but the pragmatic answer is that blood transfusion has saved far more people than it has harmed.
You could just as well say that since some people are killed in road traffic accidents on the way to the emergency room, in the event of a heart attack, the best treatment is to stay at home.