...There is plenty of bitcoin FUD that is easy to defend, but when people pull the Ponzi-card, that is when I begin to get agitated. This is because I don't have a sound argument to combat this claim.
One of the very first thing I do when I'm in this situation is asked those people why they think it's a ponzi. Maybe they've encountered some scammers offering double your BTC schemes in the past and that's what they always remember.
one should stop telling stories about unknown people from the internet, who bought xxx bitcoins when they were worth $2 and sold them on $60k each to become billionaires overnight.
This is also why some people I've met claim those returns are too good to be true and associate it with ponzi or pyramid schemes.