Do they research it to find out what is and isn't true to know for their own self? A little cognitive dissonance, perhaps? Denial?
Or do they ignore it and don't even try and find out what is and isn't real?
Either denial (as you point out) or massive distrust. Happens every day, girl finds out boy is cheater (or the reverse).
In some cases the trauma is big enough to "ruin" the person.
In the case of modern politics, I think the vast majority of people would NOT be shocked to find out the government is largely comprised of puppets and the press is totally dishonest. Finding out the elections are rigged would shock the heck out of the public though.
I've pondered from time to time if the US revolution would have happened if the King's men hadn't over-reached.
What happens to people when they find out that all the things they were taught to believe were real aren’t?
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Disbelief.
Denial
Anger
Depression/confusion.
How is history approached, afterward? In the past few decades, I have found myself reverting to dead tree encyclopedias from the 50s-60s whenever I encountered revisionism. But, now, I question those sources, too.
History cannot be fungible.
How can errata be issued for 100 years worth of events?
Well, I saw this thread, I actually read their theories with a level of sincerity. I am also open to hearing conspiracies, to a fault. There was two things that I couldn’t get around.
1) the motives on why this would be secret.
2) Some of their “proofs” are easily disproved.