I can't really think why you'd need one. Your suitcase won't be carrying any medical supplies as it's dangerous to put them in the hold. Meanwhile, with your hand luggage, unless you are taking something like two years' worth of diabetes 'stuff' with you, you won't need any extra hand luggage, so I can't imagine who on earth would 'bitch' at you because you wouldn't be going over the hand luggage capacity anyway.
The only possible issue I can think of is if you get a security guard fresh out of the academy who missed the day when they did about medical devices, in which case your bag might get a little extra search. However, with any security point containing at least 3 guards, there will be someone there who knows diabetes supplies are exempt from the usual rigmarole. For piece of mind, you could get you DSN to write you a letter on official paper stating that you need access to your medical supplies at all times, but in 15 years of flying with diabetes I've never needed this once.
On a personal level too, I wouldn't want a massive tag on my bag proclaiming that there was something terribly wrong with me, particularly as it's 'only' diabetes.