Reminds me of Terry Goodkinds 'Wizards First Rule'
"Because people are stupid, they will believe a lie because they want to believe it's true, or because they are afraid it might be true."
Although the wording from the book is quite strong, essentially 'people are more likely to believe things if they want them to be true, or if they are afraid of them being true'.
So far I have found it an important and practical lesson for many situations.
Why's that a problem? People might have good instincts, in which case they should trust their instincts as well as their reason, especially if they are stupid.
Ouch. That one hit me hard. What I would give to switch that around in myself.