Actually, Insulin is not that dangerous if you test your blood sugar levels during administration.
What is more dangerous long term, high blood sugar levels. So, a bb who eats alot of carbs compared to the average Joe, is taking more of a health risk then a bb who intelligently uses insulin. There are studies on this. Some people/non bbers, use insulin to keep their blood sugar levels down to avoid their bodies deterioration. There may be a finite amount of insulin your body can produce, so injecting insulin means that you do not use your bodies source of insulin.
There is a theory called:
Blood Sugar Theory of Aging (e.g. anti-carb lifestyle)
Insulin is a tool in that lifestyle.