Chollie, here's the reason why you weren't allowed to take your nitroglycerin pills:
Other items, such as syringes included in diabetes-related equipment, and nitroglycerine pills or spray for medical purposes, conceivably could be used as weapons, but are permitted as a medical necessity for passengers with a legitimate need.
You apparently didn't have a
legitimate need for them. Isn't it grand to know that the TSA has declared that your health is so good that you don't need this life-saving medication!
ETA: Or maybe it was because you weren't carrying
nitroglycerine pills.