Everyone has been on this tangent for years, this isn't exactly news. I think it's worth noting that the problem isn't really this simple. They concentrate the juice and pump it full of "juice" that is really just sugar. If you actually buy real pressed 100% blueberry juice, for example, instead of apple sugar flavored with blueberries, the sugar content is lower. And because you would never actually want to drink 100% blueberry juice because it wouldn't taste how you are expecting, you would water it down. Suddenly you have a glass of juice with 5 grams of sugar instead of 30 grams and you are fine. Additionally, no matter the type of juice, it is nearly always over concentrated because they are trying to boost the sugar content. People should really be watering down any kind of store bought juice.
No one is actually drinking "100% juice", they are drinking a product that resembles the fruit of juice. These companies are not squeezing juice into a bottle, they are concentrating fruit sugars and adding them back into water. The problem is just as much with false advertising as anything. I'm not saying freshly squeezed juice is healthy, but it as sure as shit healthier than the fraud they are selling on the shelves. As with everything, the problem is money. Companies know they will sell more if they say it's juice and then pump it full of extra concentrated fruit sugar.
Edit: I wish more companies sold actual 100% real pressed fruit juice, I would buy it and water it down with soda water. I also wish they were more honest with their labeling about what they are actually doing. Not everything needs to be flawlessly healthy, but we could take steps in the right direction. You should only be able to label something as 100% juice if it actually is squeezed out of the fruit and put in the bottle with no interference and additional processing.