Earlier quoted context omitted.
A bit harsh to make a blanket statement about intelligence; people just need information which isn't being readily provided or is being drowned out with too much information. The collective actions seem counterintuitive to people paying attention, but paying attention requires time - which doesn't come easily if a swath of the population is busy with two part-time jobs and recovering with reality TV in the meantime.
If you read a few books on nutrition, you will learn that refined sugar is unhealthy. This is not hard for anybody with half a brain to figure out. As for working two part-time jobs etc., many of the people doing this buy status symbols like SUVs, iPhones, big houses etc. If they didn't buy so much unnecessary stuff, they wouldn't need to work so much.
Also, the acknowledgement that sugar is unhealthy beyond children's teeth is relatively new. I don't think you'll find it in nutrition books from over 15 years ago.