The HFCS was supposed to be bad because it goes directly to the liver to get metabolized into fat...I really ought to google it.

Without pretending to be an authority on the science (which I'm not), the behavioral problems may be related to the fructose, or maybe the mercury has something to do with it. It's sort of as if someone found trace levels of lead in wine bottles and everyone went "gee! that's why wine makes you clumsy and stupid! lead poisoning!"

It's also possible that it has idiosyncratic effects on some people but not on others.