I don't agree with the reasoning presented.
It takes the estimate for the amount of energy that it takes to run the internet infrastructure and clients (141GW * 8765h in a year = 1235865 GWh), divides it by the amount of data transferred yearly (241 billion GB) and gets to 5.12kWh/GB.
You might argue that if people download more data, more equipment needs to run to enable it, but really all this energy consumption is happening regardless of my PC being idle or saturating its fiber pipes with torrents. If your website weights 14kb, all this same equipment needs to be on for my PC to load it.