I've never found a flavored "organic" or natural yogurt without sugar added. In fact, Whole Foods and Trader Joe's are filled with all sorts of "organic" and "natural" crap.
But, I digress... back to the added "sugar" in natural yogurts. It's a lot. You can do the math by comparing it to a serving of plain. 80-90 vs 150-170. That's not fruit doubling the calories, right? That yogurt container would have to be huge!
All non-artificial sweeteners are empty calories, and by and large do the same thing to your body. If you're on a diet where you don't want a blood sugar rush, HFCS, sugar, brown rice syrup, pineapple juice, cane syrup, etc. are all roughly the same.
Oh, and some light yogurts (like Yoplait) do contain some HFCS. But, I've done the math, and it can't be much at all. If you're a purist, I get why you don't want it, but if it's the cals, relax. I believe it's the smidgen that's in the token amount of fruit mixture. It's really a stretch to say there's fruit in there...
If you're adverse to artificial sweeteners, and trying to limit your calories, learn to eat plain yogurt or plain greek yogurt.
Personally, I'm okay with artificial sweeteners, so I eat the "light" yogurts at the market and add it to my plain yogurts at times.
[rant]I wish that someone would step up to the plate with a flavored, light yogurt with
minimal fake stuff. Splenda being the worst element.

Stevia tastes freeky, but a big company could figure out a way to make it work! What the F is a big bureaucracy with a lab and kitchen for, if not that? But, it isn't approved by the FDA yet (if ever), so that won't work. [/rant]