A country hot enough to require air conditioning will have an increased GDP, but this GDP is really just for bringing it to the norm of another country that doesn't require aircon. And should we count the extra economic activity generated from creating a new demand where there previously was none? 
If we optimise for the wrong thing, we end up with bad outcomes.
Ultimately, GDP isn't what matters. We should care about wealth creation, about efficient use of resources (including labor), about happiness and enjoyment.
An inevitable consequence of abandoning GDP as a measure of economic progress (as we will, inevitably do) will be coming to terms with the fact that rampant consumerism and gross inefficiencies do not constitute 'growth'
In France, it seems they are happily backing the near-total destruction of their economy. I struggle to see how this will allow them to "devot[e] more time to art, music, family, culture and community".
We need only look at the Soviet Union to see how that turned out.
One of the many reasons the Soviets failed is that they channeled a huge proportion of their national wealth into their military (fearing as they did an attach from NATO) and away from improving the living standards of their citizens.
As for environmental concerns, huge successes by the Germans seems to prove that transition to renewable energy is possible, even with current or slightly better level of technology. This may take some 30-40 years for most developed countries, and about as much after that for the rest, but we seem to have that time given successes in development of shale gas, coalbed methane, and most recently, shale oil.
Germans are good example because if they are outliers given the conditions they have, they are outliers in negative sense: they don't have much of either renewable or non-renewable resources, they are rich and need to consume a lot of the both, and cannot afford having energy too pricey because their economy is based on industrial exports so they need to stay competitive. If they can do it, everyone can do it. Others mostly don't care so far, soon they will have to.
... or propped up by governments. But then the analogy is even more broken.
Just don't expect the rest of us to appreciate being forced to do it.
To prevent that from happening, it would have made no impact if a few individuals would have stopped the harmful actions. They would have had to change the whole culture of consumption, production, even religion. See where I'm going with this?
Yes, you're constructing a "the end justifies the means" argument.
So far all Malthusian predictions of global scale exhaustion reliably turned false and in most cases, laughably so, in hindsight. This teaches us that such claims should be taken with extreme skepticism and drastic measures proposed under these claims are most probably not justified.
This, of course, does not contradict the usability of technology (or non-technology means) for greater efficiency of energy use, conservation, etc. There's nothing wrong with recycling, reuse and energy saving. It just doesn't need to be turned to extremes under the slogans of future catastrophe that would never happen.
Actually, it's a matter of dispute among anthropologists and archaeologists. A notable book came out on the topic last year that contradicts the "ecological collapse" view:
Down a slippery slope.
Nobody actually knows what happened on Easter Island. There are as many theories as there are people trying to peddle their concept of how the world will / won't end.
If I forget about the word itself (and being unsure of the cultural connotation associated with it outside France - which I have no idea of), I personally do relate to the following sentence in the wikipedia definition:
maximize happiness and well-being through non-consumptive means—sharing work, consuming less, while devoting more time to art, music, family, culture and community
I don't see men out the front with guns and dogs, demanding that I pop up to the electronics store to get the latest TV.
Or that the Buy Stuff Or Else Act 2012 had just passed through both houses of Parliament and received Royal Assent.
...so yes, I think growth has forced its way into our day-to-day lives even if you are successfully ignoring any suggestions to buy the latest consumer gadgetry.
Individual decisions only go so far - you can decide to "degrowth", but if the politics, or culture, or industries are oriented toward growth, this is pretty much a drop in the water (well until a given subject becomes suddenly important, like we saw with environmental issues in France a couple of years back).
If as a society we consider stability and sustainability to be more important than growth, then this affects a lot of our decisions: expectations of how long a given useful product should work (appliances etc), how we decide about things that are worth investing time and resources in, subjects to be taught at school, kind of jobs to be created etc.
Now a true "cultural" question: you mentioned that people should not "expect the rest of us to appreciate being forced to do it" - is that because in your country, there is an activism (perceived as negative?) around degrowth?
Honest question: I'd like to understand your initial reaction!
Any genuine attempt at degrowth will require some pretty unpopular policies. Folk like that their lives, on the whole, improve over time (modulo real estate in first world countries ... but that's another rant for another time).
So it's possible to degrowth at an individual level; but at a societal level, it would require force and cause more disruption than people realise.
And I'm agin' it.
There are indeed men with guns, dogs, and even armored vehicles forcing you to carry out most of your transactions in USD, thereby giving value to USD no matter how poorly it is being managed. Maximizing production through government spending and new money creation overdriving the economy is the thesis of Keynesian economics. What exactly does a 0.2% interest rate say about how we view preparing for tomorrow?
Although behind the scenes this may be the case, the rhetoric remains.
In the UK we still have Labour bleating about the Conservative-Liberal Democrat coalition making spending cuts "too hard, too fast" when they are barely making a dent in the annual deficit.
I don't have a problem with pursuing growth, so much as focusing on the next few years (or the next election) to the exclusion of anything else.
This 'degrowth' ideology seems to be moreso redirecting growth towards things that are more real, necessary and sustainable. Growth is fairly natural and should be expected in any healthy and free economy - not just in our modern 'advanced' juggernauts.
On a several decades/century scale it's worthwhile to funnel at least a few percent of GDP into basic science research. But, in any given quarter/year, it's almost certainly a net loss. The trick being that every few decades, you'll get nuclear power, the transistor, etc.
Or, as a 'local' example: non-trivial number theory had basically no benefit for centuries but humanity kept 'investing' resources into it - which a short term optimizer wouldn't. Then, cryptography came along and it suddenly 'paid' for the entire field a dozen times over.
: Research is sort of like early stage VC - but with funds that pay out over 70 years instead of ~7.
: I would love to write about many more examples in much more depth, but will omit for the sake of brevity. I roughly feel like the newtonian mechanics was directly responsible for the industrial revolution, relativistic physics for the nuclear age, quantum mechanics for the computer age (with similar analogues in the biological sciences).
That said -- these didn't happen all at once. And every technological upheaval, no matter how large it has been in itself, has still appeared in the larger context to be only an incremental improvement.
Or to continue the calculus analogy, you divide your spending on growth between spending that increases the first derivative and second derivative of value. The former is current short term growth, but the latter may lead to more growth in the long term.
How does a country that embraces 'degrowth' defend itself militarily from a country that is still working on the high production paradigm?
Of course, they lost to Nazi Germany, but unlike us Brits they didn't have a Channel to hide behind - after all it mainly took the huge sacrifice of the Soviets to eventually defeat the Nazis.
France has one of the highest rates of productivity per capita  and is the 5th highest military spender in the world .
It's not hard to see how a country with nukes defending itself from a country with nukes AND a conventional military could be forced to make a whole lot of concessions.
Does anyone have any thoughts on a technology tax? If say you're fired because your boss hired a robot to do your job, your boss pays a percentage of his increase in profits as a tax which is redistributed to everyone - much like in Alaska how everyone gets a check for the oil that is pulled from the ground, what if everyone got a check for the technology pulled from our minds? Maybe this would encourage people to value technological growth over consumption growth.
You're not seeing the whole picture: Being replaced by a robot is just the final step in an extremely long sequence of productivity enhancements that being with using a shovel instead of your bare hands. Why should the tax hit robots but not a power drill? Or a fork-lift truck? A washing machine? Or a computer? (don't forget, as programmers, we are parties to one of the largest eradications of jobs in the history of mankind)
What you're really proposing is a tax on increasing efficiency, by a long shot the best and most easily understood kind of growth. Interestingly, with reference to the movement's goals, little frees up more resources for family, art and music than getting the same work done in half the time.
I think the real gripe with this is that, although automated production may be more efficient, it fosters greater wealth inequality.
As tools become more powerful, and come to replace rather than assist humans, those with existing wealth become yet more powerful. The evil factory owner can now produce their widgets five times faster, at half the cost, and they don't have an unruly workforce to rely on.
These civilizational sustainability benefits are much of why I'm starting an augmented/virtual reality glasses company ( http://vergencelabs.com ). The other reasons are related to education and to transhumanism.
But I don't think we need any invasive interfaces to achieve fully realistic immersion. Optics will suffice. We still want computer vision to do AR/VR and bio as well, but we don't have to wait for transhumanism to succeed before we can start obsoleting physical goods, monuments, commuting, etc using just wearable displays and haptics.