Yeah, the language mix-up is making it hard to tell people. We "know" that the brain eats sugar and that sugar is a simple form of energy. Unfortunately this applies to glucose specifically, not to any sugar-class molecule and not to the white crystalline powder called table sugar. Glucose is ok for you. Practically every tissue in your body can use it right away. Fructose is, as you said, metabolised in the liver, and is practically toxic. Table sugar and HFCS are both 50-50 fructose-glucose and biologically equivalent.