In response to your edit, there's a lot of gray space between demonizing and letting kids have at it. I was raised on homemade, simple foods and despite loving junk food, I have no problem eating healthy stuff because that's how I was raised. If anything, certain junk food was encouraged, but because the focus was always on a traditional understanding of healthy foods, it was easy to adapt as my personal understanding of "healthy" changed. So we shouldn't demonize anything, but we should definitely teach kids that there's not really any benefit to junk food; if you really have to eat it, make it a treat once in a while but learn to appreciate healthy options.