If your religious beliefs (or more applicable to this situation, your openly declared lack of religious beliefs) will end up raising the costs of a business, it is completely appropriate for them to charge you more than other people.
I wonder if any athiest Freepers can help me out here. What would possess someone to get an "ATHIEST" license plate in the first place? I don't believe in the Islamic religion, but I don't think I would ever put "INFIDEL" on my license plate, especially if I lived in an Islamic area. Evidence from this article shows what the costs are. But what are the benefits? Taking pride in showing everyone what you don't believe in?