Well actually I'm going to go against the grain a bit here. When I was small we lived in Asia where there was very little in the way of junk food or confectionary, so I basically never had any. Even ice cream was pretty much unavailable and when it was available it was yukky. There were fizzy drinks like Coke and 7up but my mother had a thing about teeth and so I was only ever allowed to drink them at birthday parties, mine and other people's.
Fast forward a few years and we arrive back in the UK. The choice in junk food is amazing. My mum is still not keen on sweets but we are allowed chocolate in moderation plus we have biscuits in the house. I quite naturally want to try sweets like all my schoolfriends have so buy the occasionally one. And hate them. Ditto fizzy drinks, to this day I can't finish a can of Coke. All that not having it around had trained my palate towards "healthier" food and I found the cloying sweetness pretty disgusting.
Maybe it's because nothing was really actively banned so there was nothing to rebel against, but I (or my sisters) never stuffed our faces with sweets at parties or went out of our way to fill up on junk. I am a bit of a chocoholic now but only became one when breastfeeding
The way I see it is to direct young taste buds in he right direction rather than labelling any food as pure evil and banning it. My DD hasn't yet had any junk but then she's still only 18mo. I expect she will be more and more exposed to it as she gets older, but I'm not going to get too uptight about it, I just won't have it at home so it'll only ever be a treat when we're out.
BTW, in defence of Xenia, we in fact don't need refined sugar as in sucrose. Glucose is obtained by the body from carbohydrates in general, such as fruit, bread, pasta etc. Plenty of natural sugar in fruit but with the added bonus of vitamins and minerals, unlike sweets.