Overwhelm the body with anything and bad stuff will happen.
Corn fructose is used in packaged food and soft drinks because it is the cheapest way to provide the sugar, but it is also the most harmful.
Fructose is fructose no matter the source. It is no more harmful than any other sugar when consumed in moderation. It is no more responsible for diabetes than any other sugar.
There are variations in the various types of sugar. Glucose is the least harmful. Fructose, depending on what it comes with is as benign as glucose or is more harmful than glucose. Alone it is more harmful. In fruits it is generally no worse than glucose.
Wife is diabetic. We have studied this stuff rather extensively.