You know it is possible for somebody to be have a sordid and questionable history whilst also being well informed and correct on some matter. Not saying he necessarily is on this, but it IS possible.

Whether carbohydrates can drive obesity in certain people is a hot area of discussion, so I would not discount somebody for bringing it up. I think this is a natural reaction to the fact that fat has been vilified as making people fat for decades and it turned out to not be 100% true, so now people take an extremely skeptical look at the advice of eating an abundance of carbohydrate.