I think the notion of not photographing their wedding is a phony principle stand. Jesus spent most of his time with sinners - not to condone their sin - but to be a light.
I also think they are falling prey to a scam, and by not agreeing to do it, they are stepping right into the doo doo layed out in front of them.
I would go to the mat for any owner to do as he/she pleases with a business, a property, etc. And I absolutely confirm their right to do whatever they want to to and refuse service to whomever they want to refuse it.
Are you denying MY RIGHT to say it was a foolish business decision?
Far be it for me to stop stupid.