I never said I expected them to have free substitutions (wth did that come from??) or even to cater to our needs. I said that if they do, we patronize them happily at any price and in the case of restaurant, leave ginormous tips. And I don't know about diabetes but can you die within minutes from a trace of potatoes touching your food? When it's your child, and not you, it also changes the entire dynamic of the situation.
I'm sure your friend appreciates you but until you go through it with your own child you don't really understand how much food allergies can affect your whole family. It's not quite as easy as just avoiding places that aren't necessities. Unless you are happy with your child never leaving the house except to go to school or the doctor.
And to keep this on topic, I guess if a business wants to alienate 10% of the population AND their families (which probably adds up to more than 20%) that is their right but it's the right of anyone not to go there. I'm willing to guess it isn't just allergic folks that don't want cat hair all over their fabric.