The labeling of otherwise high-calorie foods as sugar-free,  based on the replacement of all sugar by artificial sweeteners, should be prohibited by law. Such a prohibition is indicated because many consumers who need to lose weight will interpret the label sugar-free as synonymous with low in calories and harm themselves by building weight-loss diets around foods labeled sugar-free.  Manufacturers of sugar-free foods are well aware of this tendency on the part of consumers.
Product labels that are literally incorrect, but in such an obvious manner that no rational consumer would rely on them, should nevertheless be prohibited by law most helps to justify the conclusion in the passage.