In arguing for the continuity in Eugene Genovese's thought, Stuart Schrader paraphrases his thinking this way:
In contrast to historians who preceded Genovese, however, he saw the social world of the enslaved and the masters as a unity, even if fundamentally cleaved. The chief difference between this non-capitalist system and capitalism is that slaveholders could not shrink their labor force without losing their investment in those enslaved bodies. In contrast, under capitalist competition shedding workers is key to maintaining or increasing profitability. Under capitalism, productivity increases are enabled by introduction of labor-saving machines, whereas to increase productivity under slavery, according to Genovese, slaveholders had to add bodies or more closely surveil and abuse the enslaved. Because the South thus lacked the economic dynamism associated with capitalism, it fell behind the North and could expand only extensively into new territories, rather than intensively, as the North did, through technological innovation.http://brooklynrail.org/2012/12/express/reading-eugene-genovese-in-the-age-of-occupy
Later on, Schrader gets into heavy duty socialist theorizing. Apparently, because a in 1751 a sea captain jettisoned sick slaves to save the remainder under the condition that the cargo was insured and the slaves not, Schrader concludes that insurance itself was at fault and that is a product of capitalism so capitalism must go.