The Collaborative International Dictionary of English v.0.48:

editorialize \ed`i*to"ri*al*ize\ v. i.
   1. to write an opinion in an editorial in a publication.
      [PJC]

   2. to insert personal opinions into an article or statement
      that is supposed to be an objective statement of facts.
      [WordNet 1.5 +PJC]

WordNet (r) 3.0 (2006):

editorialize
    v 1: insert personal opinions into an objective statement [syn:
         editorialize, editorialise]