Actually, Seraphim, there are compounds in turkey that can trigger problems for people with Crohn's disease and IBS (irritable bowel syndrome). Also, turkey is problematic for people who have kidney disease due to its high phosphorus and potassium levels. Chicken and certain cuts of beef and pork do not have these compounds or high mineral levels.
A lot of this problem between chefs and people who have problems with certain foods stems from the fact that recent advances in medical research have clarified the relationship of some ailments to diet. For example, 20 years ago, people who had symptoms of celiac disease just suffered until breakthroughs in nutritional research determined that gluten was the trigger for the problem. Eliminating gluten from the diet of patients radically improved their health and symptoms abated. Thus, we have the growth of people using nutritional methods to control their symptoms. People who had nut allergies forty years ago just died from mysterious causes until it was determined that the chemical compounds in nuts led to anaphylaxis.
Another example-I develop recipes for people with kidney disease. It's very tricky to eat a healthy, balanced diet when your kidneys cannot filter out excess minerals like calcium, phosphorus and potassium. Some meats, grains, all beans and nuts, and some fruits and vegetables must be eliminated from their diets due to the high mineral content. The build up of these minerals causes all kinds of problems and can lead to heart disease, diabetes and ultimately kidney failure.
If you wanted to have a nice dinner out with family or friends, would you want to reveal your whole medical history to some stranger chef or maitre d? I wouldn't want to. It's easier just to say you have an allergy. Most folks with these problems are very aware of the impact on their families and their lifestyles-it's a real struggle. The last thing they need is judgmental foodies scoffing at their struggles and making them unwelcome. Their money is as good as another person's.
Why shouldn't they be able to enjoy a nice meal at a good restaurant with non-ailing friends and family? Contrary to Tchef's car buying analogy, going out for a meal with friends or family is an event-the whole of which should be enjoyed, not just the food. It's not just a purchase of some functional appliance, but a whole experience including the surroundings, service food and atmosphere. Besides, a meal is a temporal pleasure, not a long term purchase. Few restaurants exist, if any, that cater to people with food sensitivities. The issues are just too broad and varied for such a business to stay afloat except maybe in some very large cities. Granting a few small requests and offering guidance to guests on what to choose seems like an accommodation that any creative chef could make if he chose to put a little thought into it.
Relegating them to being second class citizens unworthy of any consideration and treating them to public humiliation smacks of a kind of bigotry not dissimilar to barring people of color from lunch counters.