Sugar is glucose and carbs are converted to glucose. Glucose leads to production of insulin. Too much glucose leads to too much insulin production which leads to diabetes. Diabetes is basically "you have too much insulin in your body" disease.
This is the nutrition intuition equivalent of someone wearing a continuous glucose monitor and thinking that any time it goes up, it's a horrible thing that must be minimized, even when they're eating a round meal of broccoli, quinoa, and tofu.
