This also assumes the investor has no interest income, which would be unlikely. For a younger person with a big nest egg, this wouldn't be a huge chunk of their assets. But as you age you'd want to shift into less-risky assets, like interest-bearing ones.
Also, investors would probably be diversified into real estate (which generates rental income, which is taxed as ordinary income). There are tricks that can be played in real estate, of course, but there's also lots of ordinary income tax paid.
> I get to skip about $24,000 in payroll taxes that you and your employer must fork over each year.
"Payroll taxes" includes social security, which the worker will collect until he/she dies. It is also payable to the worker's spouse in certain circumstances. But you only get to collect social security to the extent you paid into the system. So if there's an economic downturn, the worker will have social security to fall back on in old age, where the investor will not.
The general point remains, but this is a highly stylized example designed to emphasize (hyperbolize) the author's point.