Rubbish. G has become a rather boring neocon, but hsi best work, Roll Jordan Roll, The Political Economy of Slavery, etc., is magnificant. There si not a shred, not a hint of racism, in thwis work,w hether of the variety that Blacks are biologically or culturaly or in any other way inferior. I defy you to find a passage than can be interpreted that way. Show me!
What made G controversial is his Gramscian thesis that the slaveowners ruled by consent as much as by coercion, that they did not maintain their order solely by brute force. That this could be controversial indicates the extent to which the discussion became politicized. It is simply false that every slave was a Nat Turner or Desmod Vesey, quivering on the verge of revolt. Slaves, like most people, accommodated themselves to their situation. Slavery could not have lasted hundreds of years had they not done so.
This was G's point, and it no more racist to say so than it is, say, antisemitic to say that Jews accommodated themselves to European prejudices in making a life for themselves under onditions of intermittent pograms and disenfranchisement. No, we were not all Macabees. We made up stories about the Golem, but mainly we put up with it, same as the American slaves. That is the sum total of G's "racism."
Maybe some people also get upset by G's pointing out that there was merit to the slaveowner's critique of capitalism, which they intended to justify slavery, but which G just means to observe draws close anothers between wage labor and slavery, hardly a point objectionable to socialists.