The belief is that Bitcoin should be the main money system in the world
This is only your assumption.
All of these ideas are written in the Bitcoin white paper.
I don't think you have ever read bitcoin white paper. There are no such claims in it.
https://bitcoin.org/bitcoin.pdfRegardless of what your assumptions may be, bitcoin is not here to replace anything or become the
only payment system that the whole 7 billion people on earth use. Bitcoin is just an option for people who want an "exit" from their corrupt economies. Those who don't want to be caught with their pants down then 2008 repeats. Those who don't want someone else's hand in their pocket or their their transactions censored.
For such people it doesn't matter how much FUD is being spread, they see right through it. Those who see bitcoin as a way to get rich quick are the ones who always fall for the FUD.