Sustainable farming has the capacity to be more productive per acre, but will generally be less productive per farmer. Resource (land) productivity goes up while labor productivity goes down.
What's the sense in pursuing any other way of farming when we have so many unemployed? (Duh, increased labor competition = decreased labor wages.) It's asinine. And does sustainable, labor-intensive farming need to be miserable? That's the argument. I would guess no. I'll be developing this more in my series on capital accumulation.