You could make the alternate case that people want to believe that "a calorie is a calorie" despite the evidence to the contrary because it means they don't need to change their habits. Defense against change. It's not surprising that people prefer the "science" that conveniently reinforces their life choices. The USDA and the food industry is also perfectly happy with the status-quo, because processed foods are a lot more profitable than whole foods are. In that sense, it's not surprising that people suggesting healthy foods are considered "radicals" -- people don't want to change what they eat, and the food industry doesn't want to change what they sell.