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..
I somehow think that what government or people who hated Bitcoin are succeeding in convincing people that Bitcoin is type of threat to our planet.So how well do you know the process of mining Bitcoin as whole like ASIC machines,memepool, hasrate,miners, cryptographic puzzles etc? Some cryptocurrencies are using POS which do not need any consumption to find solutions for block so you need to know that also.
Remaining the question of electricity consumption it has been discussed many times but in reality don't you know mining procedure have devastated environment from decades and cost of lives of many labour class.So we can also raise a question that is bitcoin taking life's of people unlike others activities like mining for metals like gold,coal,cobalt, lithium.
EV uses cobalt which is rare metal and they are exhausting it for vast consumption and destroying environment but nothing major discussion about them.Banks and other also uses high electricity consumption which is very less as compared to bitcoin.This only until 21 million coins are mined but other will still consume same or even more energy.So think about it.