It’s not demeaning. MAybe a little nit picky but I see your point. We were discussing beliefs. There are beliefs that have no foundation in a verifiable fact but are presented as the truth. 
Since we’re pulling dates out of hats, I’ll pull out 40 years. I’m old enought to write about people I knew 40 years ago. Besides, you may not logically conclude that just because you haven’t found anything earlier yet that what you have is the earliest.
I too am able to write about events I witnessed when I was young. Thing is, I would only wait 40 or so years if the events where unimportant. I would have to take a chance and say that it is fair to call the events under discussion “important.”
Memories are not the same to many people, I have a younger sister who tells us memories different than the rest of us have. She will argue that her memories are right but then 3 of us will say that is not the way we remember it and our memories jibe. So memories can be wrong.
Monavis