At any rate the glucose uptake is generally lower with fruits, even if juiced (but whole fruits with fiber still intact are best). The rate at which simple sugars enter the blood is considered one of the primary problems, as this leads to a number of metabolic problems and higher generalized oxidation of body tissue.
Unlike added sugars fruits also have antioxidants and a number of other compounds and nutrients that do a swell job at negating these effects and even providing benefits (i suppose because a lot of fruit has surplus of Anti-Oxidant to Sugar Burn.
Fruit is typically a source of fructose, which uses a different metabolic pathway to glucose. Fructose is processed via the liver and converted into glycogen for energy storage.
That said, juice is definitely worse than whole fruit as you typically use several serves of fruit for a single serve of juice. Rarely would anyone eat 3-5 whole oranges in a single sitting. The sugars in a serve of fruit are also locked in a cellulose matrix (fibre) which limits the rate of release, whereas juice is effectively predigested food lacking the slow-release mechanism of the fibre. You're going to be loading your liver with an unnatural amount of sugar, not unlike pouring a jar of honey down your gullet.
It's a reason you should avoid mixing strong alcohol and juice or fructose-heavy soft drinks - you're hitting your liver with both barrels. Add paracetamol to the mix, which in even relatively low doses is toxic to the liver, to cure the morning headache and you're going to feel very unwell.
The ratio of glucose to fructose in HFCS, honey, and most fruits is about the same. Some fruits have more glucose than fructose, some have less, but the ratio for almost all of them is less than 2:1.
So either the problem is the characteristics of a single food item (ratio of sugar, fiber, fat, etc.), some magical byproduct of processing that makes up a very tiny fraction of the food, or (more likely correct) the ratios that make up the diet as a whole. Carb/fat/protein ratio seems important as does the ratios of which carbs. Demonizing sugar or "refined" sugar seems ridiculous, encouraging proportional consumption makes sense.
Fructose doesn't satiate, while fiber does, and it slows down absorption of fructose as well.
For the same reason, fruit juice is pretty much liquid candy with vitamins.
The perfect example is that it's unlikely you'd have the appetite for eating 15 apples, but it's not difficult to drink 15 apples worth of juice.
I've never really heard anything to suggest fruit is a risk. The fiber slows absorption in the gut, so you don't get the blood sugar spike, and it seems like many issues tied to added sugar consumption trace to the blood sugar spike & insulin response.