Earlier quoted context omitted.
You are getting lost in semantics, because if you are saying: there are calories ("sugars") which make it much easier to gain weight. Then a calorie isn't a calorie.
Calories are calories (it's literally a measure of energy!) The packages they come in will effect hormonal and psychological responses differently which may affect the amount you would take in if intake is left unmonitored. To that extent, it's wise to take in foods which don't nudge you towards over consuming, but if you can be disciplined and take in a quantity of energy less than you expend on a consistent basis,…
Does our body digest things by acting like a furnace? No. There are different ways to extract energy from food and our body does things that aren't accounted for by the nutrtional facts blurb on the box. In some cases the food will just go straight through you, such as when you eat loads of fat. All those "calories" don't necessarily translate into x pounds on your body in new fat.