A few points, for clarity:
2. Most HFCS is 55/45 or 42/58 fructose/sucrose. So in nearly all cases the only thing separating sugar from HFCS is that one little bond. I still need to consult with a nutritionist, but I would guess that's the first thing your body breaks down, and at that point the sugar is essentially 50/50 HFCS.
3. As far as I know, the research does show that fructose is bad for you.
So. Most people know point 3 but don't know point 2. And there aren't many (if any) well-done studies comparing sucrose directly to 50/50 HFCS. I would love it if a nutritionist could weigh in on point 2, or point out any research directly comparing sucrose to 50/50 HFCS. But this is the story as far as I know.