http://www.dailykos.com/story/2012/04/29/1085980/-Sean-Hannity-Americans-don-t-go-to-bed-hungry-because-rice-and-beans-are-nbsp-cheap?detail=hide This is an excellent post, and covers around 40% of the food justice issue.
She has a quote from Sean Hannity that slides slowly into the fact that no, rice & beans aren't a complete nutritional choice. It may, stave off hunger but certainly isn't a complete menu. And he fudges on his statement, adding the importance of fruit and veggies and a little added meat.
Here is some nutritional data on rice (I am using white rice as an example):
http://nutritiondata.self.com/facts/cereal-grains-and-pasta/5712/2 Here is some nutritional data on beans (pinto):
http://nutritiondata.self.com/facts/legumes-and-legume-products/4312/2 Here is a little something about costs etc. of some "budget" items for menus :
http://www.epicurious.com/articlesguides/everydaycooking/family/budget_ingredients (some of the recipes seem to me a bit implausible as to budget--however, the prices do give you an "idea" of relatively inexpensive food choices...if you live some place you have a choice available to you...also, some of the prices vary greatly as to region...)
and here is a scholarly study on rice and its history...
In terms of nutritional value and value of production, rice is the most important crop in the world. For 3.3 billion people living in Asia, rice provides 35-80% of their total calorie intake. Although rice provides some nutritional value, such as protein, minerals, vitamins, and fiber, it does not provide enough nutrition to be a main source of food. Brown rice has more nutritional value than white rice. This is because the outer brown layer to the rice contains proteins and minerals. The white part of the rice is mainly carbohydrates. Rice can be stored indefinitely if it is stored in a cool, dry area.
http://www.duke.edu/web/soc142/team3/Group%20Rice/History.htm