I have personally attended a session at a conference in which a researcher presented essentially perfect prediction of disease status using a biomarker approach and had his results challenged by an aggressive questioner. The presenter was no dunce, and argued only that the results suggested the line of research was promising. Nevertheless, the questioner felt the need to proclaim disbelief in presented results. No doubt the questioner thought he was pursuing the betterment of his field by doing so.

There's just a point where if someone claims to achieve results you think are impossible, "mistake or deception" becomes more likely to you than "good science".