Opposite words for opinion:
rejection, unbelief, infidelity, incredulity, doubt, dissent, tie, skepticism, suspicion, denial, fact, misgiving, stalemate, standoff, truth, disbelief, halt, draw, distrust, deadlock.
Usage samples:
  1. It is natural for a person to try to live up to the opinion that other people hold of him."
    "Ethel Morton at Chautauqua", Mabell S. C. Smith.
  2. He and his father had a difference of opinion; that is all I can say.
    "The Grey Cloak", Harold MacGrath.
  3. But I'm not going to think now of what his opinion of me may be then.
    "Set in Silver", Charles Norris Williamson and Alice Muriel Williamson.
  4. Mr. Wemmick, said I, I want to ask your opinion.
    "Great Expectations", Charles Dickens.