Just legally park a big white van outside the convention with a vinyl sign on the side, and put something simple on it like.... "how many people have YOU shunned in order to show just how loving and christian you are?"
Or, the May '94 Awake front cover reproduced on the side of the van, and next to it a picture of a cow, with the words "No you cant have blood transfusions! You must accept an early death like these brave children did! (Unless you take it one fraction at a time. Or it belongs to this cow.)"