Tom Philpott has a response in Grist to the article, The Omnivore's Delusion: Against the Agri-Intellectuals written by a corn/soy farmer from Missouri published in The American, a right-wing journal.
Tom starts off by acknowledging the obvious issues inherent with sustainable agriculture such as these three big challenges:
1) soil fertility—in the absence of synthesized nitrogen and mined phosphorous and potassium, how are we to build soil fertility on a larger scale?;
2) labor—sustainable farming requires more hands on the ground; who’s going to work our farm fields, and at what wages?; and
3) access—in an economy built on long-term wage stagnation, how can we make sustainably grown food accessible to everyone?
He then goes on to discuss the flaws in the Omnivore's Delusion article. I'll leave you to read what Tom Philpott has to say since he's going to do a better job than I. So go check it out! And come back here and let me know what you think.