No shit.....but not all calories are created equal.
No Shit, macro nutrients are different. Try 2 grams per pound, then try 1.5 grams, 1 gram, etc and find your optimal amount. If you look at how a lot of people eat, you will see that there is a mass of very low protein foods like candy and cake, and very little high protein foods.
Alot of people don't get their RDA's.
The point of this is to find out exactly what you need and not a gram more. Then get the carbs you need, then the fats. Those nutrients can even be obtained by ice cream or candy as part of your diet, but only if you get the required amounts, which differs slightly from person to person.
However, eat all the protein you want without attention to calories, and you will gain body fat.