I agree with what Ron W. posted, which was very well said and succinct. JW's accept organ transplants with little or no issue. The reality is that a blood transfusion is an organ transplant...with all of the same risks as other organ transplants. Rejection and disease are possible in any transplant. If a JW had a heart or kidney transplant, it is almost certain that there will be residual blood transferred to the recipient during the procedure. A transfusion is no more a case of "eating" blood than a kidney transplant is cannibalism!
If you are comfortable with the stem cell transplant, you should feel ok with a transfusion, even if it isn't the "right" fraction as prescribed by JW's. Hangover guilt hangs on, and I understand....old habits are hard to break!