If I pull a potato out of my backyard garden, bake it, and then chow down, what part of that has been refined? There's as much fiber in a russet potato than there is in a half-cup of brown rice.
It might be that the cause of diabetes is glucose level spikes and therefore insulin spikes; the video that was posted here last month with the Robert Lustig from UCSF talking suggested it actually something other than insulin that contributed insulin-resistance -- free fatty acids precipitated by the liver. It's not as simple as saying this thing that has spikey behavior is going to become ignored by the body if it keeps spiking. Things that seem analogous aren't always, as much as it would make knowing good from bad so much easier to distinguish.
I won't tell you it's bad for you, but I'll tell you with a pretty damn high amount of certainty something else: both and I and you don't know it is bad for you.
Might there be a risk? Sure. But then we've spent the last thirty years believing something else, saturated fats, were more of a risk than they now appear to be. It might be possible that we are leaping too quickly from possibly correlative to sufficiently causal yet again.
There's a lot in common between the saturated fats craze of the preceding few decades, and the fervor of our new dietary crusades today. I'm not convinced that we've learned a damn thing from that experience, and thus worry we are destining ourselves to looking back on this craze the same way in 30 years. Biochemistry and metabolism just aren't that simple; making it artificially simple doesn't do crap.