if he hadn't focused (nearly) entirely on calories, and completely glossed over the subtler parts of the recommended daily intake - the author almost makes it sound as if he wants the poor to give up on vegetables or fruit entirely.

He has a point on some level of course, if your food budget per day is in the low single digits, a cheeseburger is probably the best value that you can get for one dollar. But if you're going to eat cheeseburgers on a daily basis, the long-term consequences will become a problem (and yes, McDonalds does have healthier alternatives, but those are in a different price category, at that kind of price you have far more options).