While the quantity is certainly a problem, its not the only problem, and its important that we realize that HFCS is indeed worse than sugar in many ways.
From a health perspective HFCS goes directly to the liver & releases enzymes that store fat. The fat burning process is slowed & contributes more to obesity than sugar. Also, HFCS does not stimulate insulin production, which causes us to feel full when we’ve had enough, so people eat/drink more and more (as evidenced by the enormous size cups of fountain soda now available at most concessions). Research has linked HFCS closely with type 2 diabetes. Additionally, there is preliminary evidence that HFCS may be carcinogenic.
But also from an environmental perspective, the proliferation of corn trade has devastating effects. In the US, corn subsidies have encouraged the proliferation of corn growth to dangerous levels. Where farms should be rotating a diversity of crops to promote sustainability they are increasingly economically incentivized to grow more and more corn at the cost of the environment, and as we find new ways to market all kinds of corn products like HFCS, the amount of corn in all areas of the average diet is alarming.
Please read the links I posted for more information