This is a gross oversimplification. Type II diabetes has a genetic component, but is also triggered by lifestyle factors - primarily obesity. Obesity can be caused by eating too much of anything, not just carbohydrates alone. This comes from the American Diabetes Association, and has been backed up by a number of studies.
Complex carbohydrates can also be a healthy part of a diabetic's diet. This, again, is according to the American Diabetes Association.
But as I said earlier, I'm not talking about diabetes - or at least not directly. I think the primary reason carbs have gotten such a bad rap is because the majority of carbs consumed in this country comes from unhealthy sources, including soft drinks, restaurant super-sizing, and an overall increase in the number of processed food products on the market. Rather than cut back on these foods, the nature of our society is to throw out the baby with the bathwater. Instead of reducing the consumption of "bad" carbs, the knee jerk response is to eliminate carbs altogether.