The Collaborative International Dictionary of English v.0.48:

Dogmatist \Dog"ma*tist\, n. [L. dogmatistes, Gr. ?, fr. ?.]
   One who dogmatizes; one who speaks dogmatically; a bold and
   arrogant advancer of principles.
   [1913 Webster]

         I expect but little success of all this upon the
         dogmatist; his opinioned assurance is paramount to
         argument.                                -- Glanvill.
   [1913 Webster]

WordNet (r) 3.0 (2006):

dogmatist
    n 1: a stubborn person of arbitrary or arrogant opinions [syn:
         dogmatist, doctrinaire]