The same people who say things about cryptocurrency that it's unknown for them they act like they really know all about the other things what they trust,If you ask from average person can they explain the process of creating money debt and Fiat currency...they don't know.
Sometimes, everything and people's knowledge will also depend on what media they follow. Because not all media talks about Bitcoin clearly and well. In fact, many people because they don't like it only spread about the minuses or weaknesses of Bitcoin. So, that's what these people also accept, giving rise to thoughts like that. And unfortunately, they will always believe more in the media they believe in with the various opinions they get.
My advice to people like this, tell them, it's useless for us to argue about this with them. because they will always say that what they say is true and they will always think that they know everything.