It looks to me more and more as if the Society was crazy to not just go ahead and pay the sales tax on the food and literature. After all, they had a captive audience to buy the stuff - they could have just marked up the price to compensate for the tax.
What they did instead was to shoot themselves in the foot with "voluntary contributions"...as well as the embarrassment of having to get into bed with the likes of Jimmy Swaggart to try the thing in court.
What a great messup under "divine guidance"!