They're all just attempts to simplify. Actual balanced diet and nutrition is really conplicated and has no formal fast rules. Picking an ingredient (sugar) or macronutrient (carbs, protein) and demonizing it makes the story simple, and something that someone with no interest in nutrition can follow.
"Eat all things in moderation" I think is good advice, but it's too vague for anyone to take it.
So we can expect at least a few more generations of bogus diet books before people will accept nutritionally balanced human chow, which is the true simple way to do it right. :)
Eat in moderation is good advice. The problem is that refined sugar is a recent invention that the human body is not designed to handle well. And one consequence is that it tends to fuel hunger and so steers people away from eating in moderation.
"Eat all things in moderation" I think is good advice, but it's too vague for anyone to take it.
So we can expect at least a few more generations of bogus diet books before people will accept nutritionally balanced human chow, which is the true simple way to do it right. :)