How is truth verified? There are different possible answers to what the facts are typically. For instance, Paul Revere only went a few miles to warn people about the British invading army. Israel Bissel went hundreds of miles and warned nearly every state. Henry Wadsworth Longfellow found it much easier to rhyme the name of Paul Revere than Israel Bissel for his poem about the event. Now everyone thinks that Paul Revere did his famous midnight ride and if you try to tell them otherwise you are considered an idiot.
"It isn't what you don't know that hurts you, it's what you know for sure that just ain't so!" --Will Rogers
My answer to your question is, maybe they think they are right?