First, I agree with you. I come only to defend the ability and freedom that permit individuals a choice to go "off the grid."
The distinction between the better life afforded by ever greater convenience and technology and the self-reliant life of splitting one's own firewood is in the words "able" and "necessary." Using your Facebook friend's figures, 60% of the population is "able" to survive on their own if "necessary." But taking Rand's point in particular, our "easier" life is made possible by men like Hank Rearden, yet dangles at the mercy of men like Wesley Mouch. When the costs imposed by Mouch exceeded the returns of the easier life, men like Rearden stop trading. If one doesn't have the knowledge and prediliction for self-sufficiency he is hostage to men like Mouch. The more a man knows and embraces survival "off the grid" the less willing he will be to endure the abuses of democracy.
In fairness, I must share this line I encontered early in Starship Troopers:
Carl and I had done everything together in high school -- eyed the girls together, double-dated together, been on the debate team together, pushed electrons together in his home lab. I wasn't much on electronic theory myself, but I'm a neat hand with a soldering gun; Carl supplied the skull sweat and I carried out his instructions. It was fun; anything we did together was fun.
Heinlein, Robert A. (1987-05-15). Starship Troopers (pp. 22-23). Ace. Kindle Edition.
Heinlein really said that? It flies in the face of prosperity that comparative advantage creates.
The quote would have been better stated:
"A human being should be able to learn to..."
But even then it's not entirely accurate. Even with a person's ability to learn new skills as the situation warrants, it's precisely because of my unique confluence of skills, which nobody else could learn, that made me so valuable at my job, while others were relegated to delivering mail and managing portfolios badly.
Am I "hostage" to the grocery store, because they supply me with pork? Or are they hostage to me and other customers?
"The direction of all economic affairs is in the market society a task of the entrepreneurs. Theirs is the control of production. They are at the helm and steer the ship. A superficial observer would believe that they are supreme. But they are not. They are bound to obey unconditionally the captain's orders. The captain is the consumer." - Mises, Human Action