Needless to say, those people are fuckwits. This is coming from someone who absolutely despises Earth Hour.
Not a fan of meaningless, do nothing events myself. But they're still better than mean spirited, meaningless, do nothing events.
If it was purely benign, then I'd agree. However, however there are now quite a lot of people who genuinely believe that not only does turning off a light translate directly to a few less grams of coal being burned at the power plant, but also that turning off the lights and burning oil-derived paraffin candles is actually good for the environment.
Now an Earth Hour that would actually make a real impact, both in terms of actually reducing pollution and giving people a more realistic taste of the sacrifices that'll need to be made if we're to get a handle on climate change? Actually shut down a few power plants for an hour, let people see what it really means to use noticeably less electricity. Not during a time when everyone's at home and has nothing better that sit around feeling all smug about themselves, either. No, do it during either morning or afternoon peak hour. Especially in a major city, where lots of people rely on electricity fuelled trains to get to/from work. Now that would be a real, actually meaningful Earth Hour. Though for some crazy reason, I'd wager all of the armchair hippies would suddenly become hard core climate change deniers.