1) this claim is much weaker than "Sugar is the worst substance for public health ever. It's literally poison."
2) and it can be a good idea if otherwise someone would suffer from caloric deficit dangerous to health and eating more food is not viable (yes, this situation is unusual)
Its hyperbole meant to convey a sense of how bad sugar (particularly added sugars) is to the health of the population. Sugar is in everything (more hyperbole!) in the U.S. America by and large is addicted to sugar and it’s very bad for us. Everything is over sweetened. Can’t even buy bacon without sugar added in some form or other.
Anyhoo. Yes sugar can be good and sugar can be bad. "It's literally poison and worst thing ever" does not productively move the needle of the conversation, almost regardless of interpretation.
This is in contrast to carbs in general, and to protein and fat, where some level of each is useful in the diet and provides a reduction in mortality and CVD risk.
As far as I know, it could be useful in case of huge need for calories.
Which basically never happens with modern lifestyle. But I guess may apply to firefighters working for several days or soldier lugging around piles of equipment.
But unlikely to apply to anyone reading HN. Unless they climb Mount Everest for fun, or volunteer as firefighters or are unlike enough to end in a war zone.
If you need to rely on hyperbole/lies/propaganda then I am going to assume that you have no case.
Long bouts of exercise like a marathon or the Tour de France or medical conditions like diabetes are the only exceptions I can think of where you'd want to instantly flood yourself with glucose.