“One of the saddest lessons of history is this: If we’ve been bamboozled long enough, we tend to reject any evidence of the bamboozle. We’re no longer interested in finding out the truth. The bamboozle has captured us. It’s simply too painful to acknowledge, even to ourselves, that we’ve been taken. Once you give a charlatan power over you, you almost never get it back. So the old bamboozles tend to persist as the new ones rise.”
-Carl Sagan
-Carl Sagan
A lie repeated over time becomes believable because we are creatures that finds comfort within our habits or what is known to us.
We could learn, or assimilate, new information but that would require time/effort which we don't have. It's much easier to "fallback" on what is known to us.
"If you tell a lie big enough and keep repeating it, people will eventually come to believe it."
-Joseph Goebbels
One of the first thing a new Dictator does is take over the media in order to control the message shared with the people. Always be careful of those that have an invested interest in having you think a certain way. If you feel like you're being brainwashed then you probably are which is your cue to stop listening.
"There are truths which are best recognized by mediocre minds, because they are best adapted for them, there are truths which only possess charms and seductive power for the mediocre spirits..."
- Friedrich Nietzsche
Any entity that spreads misinformation or encourages division in a society needs to be silenced not by an enforcer (who could enforce such a thing?) but by the masses. This means that we, the people, need to develop the skills necessary for the identification of those bad actors.
Remember that lies must be repeated in order to become believable...