In the world at large, people are rewarded or punished in ways that are often utterly random. In the garden, cause and effect, labor and reward, are re-coupled. Gardening makes sense in a senseless world. By extension, then, the more gardens in the world, the more justice, the more sense is created.
It does kids no favors, and sets them up for a potential lifetime of poor health and social embarrassment, to excuse them from family meals of real food. Everyone benefits from healthy eating, but it is particularly crucial at the beginning of life.
The bottom line is that the human body is complex and subtle, and oversimplifying - as common sense sometimes impels us to do - can be hazardous to your health.
The most common objection that I hear to walking as exercise is that it's too easy, that only sweaty, strenuous activity offers real benefits. But there is abundant evidence that regular, brisk walking is associated with better health, including lower blood pressure, better moods and improved cholesterol ratios.