It's not like the capital just fell into his lap from a friendly Wall Street banker. Those businesses are ALSO self-started (to the best of my knowledge), especially his Youtube success. He's a prime example of someone working hard, spending less than they earn, accumulating resources, and then expanding that into ownership of the means of production as well as employing others.
It's not for everyone. Sure, most people have no appetite for the level of risk involved even if they can scrape together the money to buy some revenue-generating asset (I know a guy who left the Marine Corps as a truck driver...moved back to Japan, bought a truck, and then opened a moving company). Most people don't have access to capital....nor will most people ever have the intellect to write tight software code, no matter how many government-backed Code Bootcamp Initiatives there are.
To bring this back to the original point though, telling someone to bootstrap a factory, which is demonstrably doable in the American economy even today (for flexible definitions of "factory"), shouldn't ever be a "controversial" piece of advice. Especially on an pro-entrepreneurship site like YC/HN.