Earlier quoted context omitted.
From a strategic perspective grain is the most important thing in a food shortage. People can live a year or two without fruit or vegetables, but without the calories in grain things will get violent fast.
I'm not going to dismiss it outright, but I am mild-to-medium skeptical of this theory. Take a look at some of the recent years of subsidies listed on https://farm.ewg.org/region.php?fips=00000&progcode=total&yr... . It's not just that we prioritize feed crops more than oranges, we also prioritize feed crops more than potatoes and root vegetables. Our corn subsidies are on average over twice as high as our wheat subs…
Root vegetables don't have much calories. So this would actually make sense.