The fact is that everyone is entitled to their own opinion, that they call Bitcoin a ponzi scheme doesn't change any thing about the originality of Bitcoin. Such people have little knowledge about how the Blockchain technology works, they need to be enlightened
Really friends, many people around where I live talk if Bitcoin is a kind of SCAM.
But if if they are explained about the progress of Blockchain then I make sure they will not be able to study in one month, because to learn all cryptocurrency it requires extra patience.