blasphemer

from WordNet (r) 3.0 (2006)

blasphemer
    n 1: a person who speaks disrespectfully of sacred things

from The Collaborative International Dictionary of English v.0.48

Blasphemer \Blas*phem"er\, n.
   One who blasphemes.
   [1913 Webster]

         And each blasphemer quite escape the rod,
         Because the insult's not on man, but God ? --Pope.
   [1913 Webster]