The claim in this movie is that food prices are high because of the food shortage. Because of the shortage, one can expect rising prices and it becomes interesting to speculate on food. In the developing world where about 60-80% of the income is spend on food, high food prices are pretty bad for the urban population that needs to buy food , but should be pretty good for crop farmers who can get more money for their production (not pastoralist see http://www.catherinepfeifer.blogspot.com/2011/10/some-good-explanations-on-economics-of.html). This movie shows with the example from Kenya that this is not the case. It is just the middle man who brings food to the market who will make more money. Similar patterns can be found in Ethiopia, check http://catherinepfeifer.blogspot.com/2012/05/enhancing-market-information-really.html)
Following the argumentation of this movie, high food prices are just bad for producers and consumers and a relatively simple solution (compared to implementing complex and possibly market distorting regulations) would be to produce more. And in many region of Africa, one could improve on productivity with relatively low inputs. But increasing productivity is a matter to bring the right technology to the right location and the right people as well as addressing impacts of climate change. No wonder that today, many new research projects focus on sustainable intensification options and climate change adaptation for Africa.