The threat is in the form of increasing global warming which results in climate change. Generating Bitcoin requires a capable computer to solve complex mathematical puzzles and high electricity consumption. so that some countries prohibit mining for several other reasons such as in China and Iran some time ago. if so will bitacoin and others be able to run forever or is this just an excuse to change the green field to red..
How about?
Continous growth of car numbers which do make even more our air poluted?
Generating more plastic which cant really be decayed?
Etc.
Energy issue on Bitcoin is just a bullshit excuse just for those non coiners to focus on for them to create something to counter on bitcoins existence.
They dont even consider those current things which are giving more threat on mother earth.
If they do mind much about being green then they should find out to solve first those old issues that we cant resolve until this very moment.