Not so.
By far, most people I deal with in this regard are completely sincere in their beliefs.
Somebody who doesn't know the facts will sometimes just construct a scenario that works for them, usually something just absorbed from the environment/Zeitgeist in some way, but sometimes something they assemble in their own minds. These beliefs--again, quite sincere--become nearly indestructible.
I wish it were as simple as "lying." A liar knows the real facts and believes them, he's just trying to deliberately steer others away from them. A believer can tell you 2 and 2 is 5 and pass a lie detector test.
Try arguing physics with Johannes sometime.