Wheat contains gluten which is poisonous to all humans (mildly, and no, not just to coeliacs). It's pretty well known that practically all grains evolved mechanisms to defend themselves against animals that eat it. Wheat is one such grain.
Eliminating all grains is a better way to go, but a wheat free diet is a component of what a coeliac would eat, and what is more healthy for humans.
It also has the benefit of helping correct the imbalanced caused by the "food pyramid" that emphasizes grain over fruit and vegetables. Grain is mostly carbs, and partially fibre. It's not something you should ever eat in the high volumes suggested by the food pyramid. If you abide by a wheat free diet you will create and artificial restriction that will force you to eat a healthier diet containing the remaining food groups (fruits, vegetables, diary and meat mainly - not so much the fats and oils and sugars).
Elimination of all grains is better for you than all wheat, but elimination of no grains is definitely worse.
Are wheat free diets a fad? Yes, but gluten free or grain free aren't
Do they work? They help, as above
Have you done this? No, but I don't eat a lot of grain and I know a lot of people who eat gluten free
Who is the right one in the debate? Both are partially wrong, as above
Will you try this after listening to this? No, anything that is a best seller is unlikely to be scientifically valid
Are we going too far with these diets? Dietary intake needs to be reassessed as new information is gathered and research is performed. Fad diets may be a knee-jerk reaction, but they are probably a valid step towards forming new dietary habits - eg if you want to cut down on carbonated drinks, then why not cut them out for a few weeks until you loose the addiction.
Is this a diet at all? Yes, it defines rules as to what you should eat, it is a diet.