how it is possible to describe leaders like Rockefeller, Vanderbilt, Carnegie and J. P. Morgan as both "robber barons" and "captains of industry

What two different approaches did the knights of labor and the american federation of labor take in building a union organization? a) the knights of labor accepted only unskilled workers; the american federation of labor accepted only skilled workers. b) the knights of labor accepted skilled and unskilled workers; the american federation of labor accepted only skilled workers.c) the knights of labor refused to accept african american or chinese workers; the american federation of labor accepted all workers.d) the knights of labor accepted workers from a single industry; the american federation of labor accepted workers from several industries.