Usually I agree with your views, but you are of course completely wrong.
You are a man of principles so I'm sure you can understand his point of view?
Imagine you were in his job and the bus you were asked to drive had BNP posters all over it? Would you agree to drive that bus or would you stick to your beliefs and ask the company to find another bus for you to drive.
I'm an atheist but I support this fella. It seems that you are more guilty of religious intolerance than him on this one: chastising someone for having beliefs and not wanting to undermine those very beliefs by driving a big mobile advert questioning them.