I think his point was the 9 passenger limit of Part 121. I would argue that if 9 is safe why not 14 or 18?
There was a time when you needed 3 engines and 3 flight deck officers to cross the ocean.
It's a question of how many fatalities per year you're willing to accept. If 18 are okay, why not 50? Or 180? 550? You have to draw a line somewhere.
There's a certain risk of pilot incapacitation per flight, as well as some other benefits of two pilots. Similar to the case single-engine vs. twin-engine. Engines are powerful enough that any aircraft smaller than an A320 could run on a single engine. Twin-engine oceanic crossings only became acceptable when their reliability was high enough; single engine passenger operations remain limited to small aircraft as long as engine failures remain relatively common.
But how are you going to increase the reliability of pilots? Or alternatively, how are you going to convince the society (and the regulator) to accept more passengers on a flight with a single-point-of-failure? Large crashes continue to get plenty of media attention. Smaller aircraft crashes usually don't even get nationwide coverage, or only for very limited time. The dividing line appears to be ~10 passengers. So IMHO, the only option is to provide an electronic backup pilot.