it's not a good theory, or practice, even if it did apply to everyone. we live in a society, not some dog-eat-dog nightmare-fantasy hellhole.
The sentence was not advocating the theory as a good theory... just one that would have to be equally applied to all. If the rule applies to all you have the possibility of the masses deciding that it is a bad rule - a Lockean apprach, if you will. If the rule applies only to most (those not in power), while protecting those who have wealth and/or power, you're living in a Hobbesian dytpoia already. The soverign is simply a cabal of power interests rather than a single monarch.
"i'm alright, fuck you jack" is not a sustainable ethos for any individual and certainly not for a civilisation. it's a psychopath's creed and psychopaths are at best parasitic on society if not outright destructive to it.
Now you've run completely off the rails. Of course it's a sustainable ethos, at least for historical measures of sustainability. That is the basis of countries, states, municipalities, and neighborhoods. Sure, you can build some social network to mitigate it, and there may be some charitable efforts to compat it, but reality is still still "we're alright, fuck you jack" to an astoundingly large degree.
Feel free to disprove that by donating deveral hundred dollars to Nepali relief efforts. Or any international relief effort for that matter.