People like Alan Simpson and Rick Santorum want to cut Social Security benefits because, as Simpson says,
It was never intended as a retirement program. It was set up in ‘37 and ‘38 to take care of people who were in distress -- ditch diggers, wage earners -- it was to give them 43 percent of the replacement rate of their wages. The [life expectancy] was 63. That’s why they set retirement age at 65.
This is a lie.
Source: Social Security Administration
I've heard people say this for many years, and none of them appeared to take the time to figure out whether it was really true or not.
As for the charge that our social safety net is a "Ponzi Scheme", it's a silly slander. Every insurance company works this way. There is always a group that gets benefits and a group that doesn't. If these people are the "smart" ones trying to fix our system, I have serious misgivings about what's actually going to happen when the non-smart legislature gets involved.