hmmm as a contractor I and my fellow workers seem to be right most of the time. Perhaps its the approach you take. After all, how would it look for a manager to hire contractors that are always wrong??? Most if not all managers hire contractors to provide right answers and keep them on the path to success.
The situations I have seen where contractors (rent a techs) seem "wrong" is that they didnt do their background analysis of the situation. Carry over memories from previous facilities often are mis-identified as problems at a new place of work.
We have all seen or heard about the RAT that screams safety concerns or pending doom, and then states he was let go because he brough the issues to light..etc. When in reality, there may have been some seed of truth in the matter but the guy was just basically a nut case or had some serious issues, and his wacky behavior obscured the real issue, resulting in a his loss of trust and credibility.
If you prepare a case, define the real problems and workable solutions you will be get ahead. It works every time, and if you are right in your cause, you can act wacky about it and be perceived as "passionate about his work." Employers and managers like that.. champions for a better situation.. they dont like "nay sayers of doom and gloom."