You walk up the aisle and receive what appears to be bread and wine, but which is really Christ’s Body and Blood. Why are you eating somebody’s body and drinking his blood? An indelicate question, but still, why?
Anybody who does laundry can tell you that one of the hardest stains to get out is blood. Why would anybody think you could clean things with blood? The answer is that it depends on what you are trying to clean.