To save social security, we need a combination of a payroll tax cap increase and a retirement age increase. That's the (sad) truth of the matter, and there's nothing hard-right about it. The means testing thing is unnecessary, but it's not something I have a problem with and it does not constitute privatizing the system.
Sanders (along with most of the rest of the democratic party) needs to stop spewing this "hope for the best" rhetoric and realize that SS will eventually become insolvent if we don't raise the retirement age (unless we just want to keep raising taxes to no end, which doesn't sound like a good solution). It's not a nice thing to do, sure, but it's a fiscal necessity.
The payroll tax needs to be replaced with a tax on speculation, after which the retirement age can be slightly reduced.
tax on stock investment? Don't we already have that with the capital gains tax? And reducing the retirement age will only make things worse.