I'd really like to know because I DID the research over the last two decades and you sir, are 100% WRONG.
We currently waste 95% of the resources we use because of waste in the chain somewhere. That means we could extend it 20 times if we eliminated that.
We currently use the wrong technologies for dozens of global systems where much more total benefits could be had for much less energy and resources and MUCH MUCH less money. Think of that money as what's keeping us in debt. There's your libertarian gains.
The technology encroaching us right now is set to deliver many more forms of advancement. Think of the 90's when everyone had 4-7 pieces of electronics in their living room for TV and tunes. Compare that to the 'single device does it all' of today. Now think of how many wasteful power supplies were just eliminated, with each one losing up to 30% of the power just to make DC internally. Compare that to simply recharging that single device instead.
For every single aspect of society, there are massive changes that could be made if only we could get rid of this stupid paradigm of letting mega-corporations maintain a monopoly on their field.
I challenge any comers to show one system where it's not sustainable to support 12 billion people. That's the point where it gets sticky, but don't worry, barring some massive change, the global population will peak around there and settle back to the 6-8B range.
So, who in their right mind would take these lunatics seriously? Well, how about ONLY people in their right mind. Obviously, people who don't know what they're talking about simply call them names.