We don't have any issues with sugar per se. What we do recommend against is consuming sugar, added sugar and all sweeteners in any significant quantity.
Artificial sweeteners should be avoided in any quantity. The quantity you consume includes not just the known sugar you eat but also the foods that have added sugar (corn flakes) vs natural sugar (a grape). Lots of snacks (even seemingly healthy ones) have added and natural sugar like dried fruit. 1 teaspoon of total sugar per day (added or natural) regardless of what kind it is, is unlikely to pose any serious long term health risk. The problem is sugar, corn syrup and things that quickly convert into glucose (white bread) is hidden in everything we eat.