Louis: Can I suggest to you that to alleviate any further feeling of social discomfort at the idea of declining a photograph, you have business cards made up which explain precisely that and at the end of an interaction with a person with whom you've declined to be photographed, you simply hand it to them and walk away. They'll read it later, and will understand then that you meant no disrespect or harm, and will also understand the same is true of other celebrities.

Yay, social education! :-D