They are actually making a very powerful point. A regulator is expected to at some point operate from an "external to industry" perspective. Much like a test framework or testing harness must exist out_of_band of the system under test.

A regulator that regularly pulls exclusively from industry insiders should raise eyebrows. Now whether the SEC actually pulls the majority of hires from industry insiders, that's another question I can't readily answer. Don't have those figures.