Ideas on how to argue for abolition of retirement pensions?

When discussing evils of governments with people, one issue keeps popping up - “but the government provides for the old!”.

While I have a lot of arguments, like the government’s stolen from these old when they were young, preventing them from saving for themselves; or that in a freer economy people would have much more money to spend on charity, this usually sounds too feeble, resulting in people believing I am just a cruel person.

The question is: has anyone found a punchline, a very strong and quickly acting argument for banishing (mandatory) government-run pension plans?

PS: it is a separate issue how to implement the transition away from mandatory pension. Personally I believe in a gradual transition.

And social security is a Ponzi Scheme

The wealthiest age demographic in society is the old. They have more money and more free time than people who work.