I like what the Ayn Rand Institute said about it in 2009:
The lights of our cities and monuments are a symbol of human achievement, of what mankind has accomplished in rising from the cave to the skyscraper. Earth Hour presents the disturbing spectacle of people celebrating those lights being extinguished. Its call for people to renounce energy and to rejoice at darkened skyscrapers makes its real meaning unmistakably clear: Earth Hour symbolizes the renunciation of industrial civilization.
I called it onanistic vileness, as it is a childish exercise in mutual gratification amongst the self righteous who have the luxury to choose to spend a short period of their comfortable lives deprived of a light bulb, a car or maybe something else they take for granted.
Children are starving in gulags in north Korea today. Tens of thousands of them, like concentration camps, whilst most people think north Korea is a bit of a joke.
Millions of people every year get electricity to power a light enabling a child to read a book at night.
Billions of people right now are alive because electricity and man-made energy enables them to be warm, to be fed and to be sustained.
To hell with Earth Day. Yes, pollution kills. Yes, it is important to not destroy the environment that sustains us all, but that isn't achieved through the worship of non-production, non-technology and de-industrialisation.
However, those who propagate Earth Day are at best hypocrites, like the jetsetting, big house owning, big mouth propagandist Al Gore, and at worst destructive towards humanity, like those waging war against genetic engineering.
Abstain from consumption if you wish, but don't pretend that asceticism towards energy use, technology, production, mining or the like is doing anyone any good. If you want look after the environment, look after your own property and campaign for property rights to be expanded, and against the abuse of the commons because they are the commons.
For those who cite science as the basis for their policy misanthropy, are more often than not as much (if not greater) abusers of science than those they condemn.