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..
The fact is most of the things poses a threat to the environment. Microplastics in your toothpaste or even the small plastic bag that we get from wallma often..be it cars or be it big companies making necessary products. The whole concept of nonveg meal and even a simple milk. Now what people are doing here is , highlighting just one problem because they see other alternatives which do not require heavy mining machinery but forget that Bitcoins will stop being mined after a small amount of time but the long term effects of other cryptocurrencies are strictly the same.
Now they want to deviate the people but rather they should think about asking people to use renewable sources of energy. They can integrate it with their machines and viola ! Probelm solved.