I find that reasoning to be ridiculous. According to its proponent, the
reason for disappearance of middle class, is that a certain arcane
"federal overtime rule" was not adjusted for inflation.

This makes no sense. We live in a capitalist society where wages, for
the most part, are formed in a labor marketplace.

If workers bring a certain incremental additional value to employers,
then their wage would reflect that additional value (the extra amount
that the employer would earn from hiring an additional worker).

Workers with scarce skills or who are highly profitable, would command
appropriate wages, that would rise as the marginal effect of
workers on profits increases. That happens with or without overtime
rules.

Overtime rules were not designed to distort hourly wages. They were
designed to push working hours closer to 8 hours per day and to
increase employment. It is more profitable for almost all employers to
have 4 workers work 10 hours per day, than to have 5 workers work 8
hours per day, with the fifth worker bring unemployed. The overtime
rules push employers more towards employing five workers at 8 hours a
day.

All kinds of regulations, of labor, salaries, wages etc, brings about
distortions in the marketplace that cost the economy money. It is
possible that the value of good social changes offset that cost, but
we should be clear on the existence of that cost.

In addition, when costs of transportation of goods or services are
low, jobs can move to countries with less regulations or lower costs.

I can emotionally understand why that billionaire campaigns for $15
minimum wage, but his reasoning does not stand up to scrutiny.

i