Obviously the key is "nothing but" but no one in these various threads has argued that the existence of exploitation in other relationships negates that which exist at the point of production. Then again, most of the heat is precisely on the conditions of that imbrication. If exploitation is restricted to that which can only occur in the labor process and in so doing points to what has to change in order to eliminate, then all of forms of inequality are auxiliary oppressions functionally or contingently produced by capitalism and as such will cease with capitalism's demise. This is the old class-is-supreme argument. And there's lots to recommend it since defines precisely what is at stake, economically.
But I keep getting drawn back to another tack - that exploitation is far more generalized and that it generate relatives advantages and that it drives political or power struggles among various groups and only some of those struggles and some of those groups can be covered by a theory that makes the extraction of surplus value the key to it all. And in the familiar refrain, some or many of these struggles are shaped but not caused by capitalism. And finally, presuming that capitalism has an inordinate affect in defining or shaping these other groups and struggles, the path to mobilizing cross-group alliances will have to occur, as someone mentioned, in baby steps.
Which is why reparations is so important. Whatever its outcome, cross-racail alliances or even the elimination of racialized groupings can only occur if the conditions of the inequality represented by those intergroup relations, the various forms of exploitation, are overcome.
DB