Fruit itself probably does not wreck your metabolism. It is theoretically possible since it has fructose and fruit has higher sugar than vegetables and any other whole foods. But there is no evidence that fruit alone caused diabetes. Of course, things have changed a bit now, since all fruits are sweeter, bigger, and pack more fructose per gram than ever before.
Having said that, how many people only eat fruit and abstain from grains and other forms of sugar, what Dr. Lustig might call "exogeneous sugar." Very little, if any. We probably have the Kitavans and other Polynesians who were not exposed to gluten flour and exogenous sugar.
But consider a Joe Sixpack who wants to dig into his slice of apple pie: pie fillings filled with sugar, gluten crusts, and lots of exogeneous sugar. What you ate is toxic sugar explosion, not any fruit. There are very frew "fruitarians" in the West that are eating just fruit, veggies, and meats. The minute you mix fruit with gluten or exogenous sugar, you magnify the toxidity of fructose, whether deriving from whole foods, artificial sources, or from exogenous sugar. That's the argument.