There are a couple of things I would do in this situation, firstly, I would remind your friend that a "Ponzi Scheme" was actually carried out with fiat currency, not crypto currency. Secondly - some people are just ignorant, if they are not going to get it, its OK. the same people probably have those pulse dial telephones at home and cant figure out why nobody calls them anymore. There are plenty of open minded people in the world, sometimes you have to let a few of the naysayers go.