You said it yourself you have no idea about nutrition and you clearly have no idea how the growth of the human body works. So let me explain it for you cus you clearly don't get it.
Growth rate at infancy is the fastest of any time in a human life, protien is for building tissue, muscles and general growth. Understanding this you can see protien needs would be higher then a full grown adult who has little to no growth needs except for maybe a little muscle gain. Ask any doctor who actually knows how the human body works and they will tell you the same, Infants have the highest protien need per calorie of any growth stage in the human life.
Breast milk, the perfect baby food, is about 6%. Knowing this you can easily come to the assumption that most full grown adults need somewhere around 2-6%, anymore and you are just overloading your body with extra protien it doesn't need. this can lead to many problems.
I guess I find that sounds too simplistic. It could very well be right. But if the calories/weight requirements for babies are higher than adults, wouldn't that mean that at "normal" caloric intake, babies would be getting more protein than an adult eating a "normal" amount of calories at 6% protein?
I guess it doesn't seem self evident to make the conclusion you're making to me, based on the little I know, and what I've read in this thread.