His position seems to be weak because if the inner cities were being under-recruited a team would be able to take advantage of that, recruit the creme de la creme from the inner cities for their organization and win world series after world series, and other teams would copy them or suffer through losing season after losing season, and the market would naturally correct that so his argument is not particularly strong. You would need a competitive market for that to work, but baseball is a hell of a competitive market-anything with as much money involved as major league baseball is bound to be highly competitive.
On the other hand, there might be a barely tapped source of talent that major league baseball is stupid not to develop by investing money into little leagues and such-though that raises a bit of a collective action problem as its probably not worth the money for any one team to make the investments necessary to develop that potential source of talent.
Its not exactly what he said, but if you change his comments to say baseball would raise the talent level of the game and quality of baseball, make the game more competitive and probably increase its popularity nationwid (but especially in African American communities) by investing in those communities and this would all make baseball better off-that is a defensible position.