A little sugar is not going to harm anyone. However, the quantity that most people consume (on average, 150 pounds per year) is much more than our bodies can handle.
It's not just in cookies, candies, soda, and ice cream. Sugar is showing up in many unexpected places. For example, hamburger buns. Of course, it's in ketchup and salad dressing. Each contains about 25% sugar.
If you would like to see how much sugar you consume by drinking one soda per day, take a peek.
So, yes, sugar in large quantities is most definitely a toxic substance.