If you were in my shoe, what would you've told a person that says bitcoin is a ponzi scheme created to scam people?
Either of these two I would do, depending on my mood at the time of the conversation —
1. Ignore him (if I'm in a foul mood)
2. Tell him to google Bitcoin (if I'm in a good mood).
Listen buddy, Bitcoin has gone past the era of trying to convince individuals (a shrimp) to buy in. Possibly, all they will buy won't even be up to a single Bitcoin. Institutions have already picked that idea of Bitcoin up and are buying big time. That's what matters.