The Collaborative International Dictionary of English v.0.48:

Exclusivist \Ex*clu"siv*ist\, n.
   One who favor or practices any from of exclusiveness or
   exclusivism.
   [1913 Webster]

         The field of Greek mythology . . . the favorite
         sporting ground of the exclusivists of the solar
         theory.                                  --Gladstone.
   [1913 Webster]