The problem is that when you are leaning towards believing something anyway and find out that you were being lied to about it, you don't become more critical of all information, just information that is in conflict with what 'seems' right to you.
It is a terrible side-effect of doing things like teaching kids in the 80s and 90s that marijuana was a terrible drug because when they find out it isn't, then everything else they said is suspect and any authority that tries to say anything about drugs gets treated with suspicion.
In line with this, using fear of the worst possible outcome in order to scare people backfires heavily if it doesn't happen because then convincing them of anything related to that subject again is going to have to come from a completely different source and direction.
It is a terrible side-effect of doing things like teaching kids in the 80s and 90s that marijuana was a terrible drug because when they find out it isn't, then everything else they said is suspect and any authority that tries to say anything about drugs gets treated with suspicion.
In line with this, using fear of the worst possible outcome in order to scare people backfires heavily if it doesn't happen because then convincing them of anything related to that subject again is going to have to come from a completely different source and direction.