..."none shall pass my lips" brigade who insist on different ovens/plates/forks...
try telling that to a coeliac whose "gluten-free" meal was prepared in the same area as regular pizza, bread, or other wheat containing food. Been there, done that. Not a pretty sight (or smell in the bathroom afterwards)
Or a peanut allergy sufferer who is in anaphylactic shock because they had traces of peanut on a spoon to stir their meal.
That's not religion. I know you mean the crazy fad-dieters here, they annoy me as well. Makes things really difficult for those us don't have a choice when it comes to certain types of food.