I haven't heard the clip but if the comment is that there are similarities in the way it is financed then that would be the same as any other insurance program (which is what SS is) as well as almost all pensions. With al of these programs the $'s paid out to you are not the same $'s you put in.
This is the only similarity to a Ponzi scheme but that doesn't make it the equivalent of a Ponzi scheme
Listen to the clip he says:
1. There are STRONG similarities to a ponzi scam the main one being intent;
2. SS trust fund is a fiction and bankrupt now;
3. Takes will have to double, triple, or even more to even remotely keep current promises and young people are going to get fucked royally.
That is a scam no matter how you put it.