| You have a disease that directly affects carbohydrate metabolism...therefore it can be argued that any carbohydrates you consume are not "helping". There are entire treatment modalities available today that are based on elminating as much carbohydrate as possible from the diet, and some are actually modestly successful.
Of course, for a normal person who does not have a disease that affects carb metabolism, eating "sugar" is no big deal assuming they are not exceeding their energy needs with other foods as well. And if you take that thinking one step further, a diabetic who is on insulin and who knows how to carb-count should be able to eat any carb ("sugar" or otherwise) with some assurance that it is "safe".
The problem with "candy" as opposed to potatoes or corn, etc., is that there is no nutritional value in it. Empty calories. No vitamins, minerals, fiber, protein or other nutrients of any value. So for a diabetic, a person with a metabolic issue with carbohydrates, when they consume candies and "sugar", they are suffering a double-whammy of sorts: a blood sugar rise for no return. Except maybe making your mouth feel good (which I would say is okay occasionally).  | 
