Many years ago I figured out the following.
Nothing makes people as mad as the truth which they either, A) don't want to be true, or B) don't want anyone to know is true.
Related to this is that the more people vehemently claim that something is false (and the madder they get when confronted by people who claim it to be true), the more likely it is true.
However, that has been known (at least by a few intellectuals) for centuries.
"The lady doth protest too much, methinks." - Shakespeare, William. Hamlet.