The inability to escape bias does not mean attempts to minimize its impact are useless. I frequently see people making the same argument Arrington is, and I'm always astounded by the sloppiness of their reasoning.
People say they want to know the reporter's opinion, but the thing is, it's relatively unimportant information. The reporter's opinion is nowhere near as important as the facts of the story in most cases. The reporter is just some guy whose opinion is worth about as much as anyone else's. His value to me is in the quality of his information-gathering and his explanation of that information. In an opinion-based piece, these take the backseat to proving the writer's thesis, which does me little good.