The retiree example is intended to demonstrate that a wealth tax is inherently perverse, regardless of who is targeted. Savings are just deferred expenditure and debt is just expedited expenditure. When you tax wealth, you expedite consumption.
Another way of thinking about this: A wealth tax is like inflation, except assets are also devalued alongside your savings. Which means the wisest strategy is to consume now, save nothing, invest nothing.
50 dollars tomorrow may be more useful to you than 100 dollars today if today you'd only buy useless crap for it but tomorrow there is a brilliant investment opportunity.
Another way of thinking about this: A wealth tax is like inflation, except assets are also devalued alongside your savings. Which means the wisest strategy is to consume now, save nothing, invest nothing.