People do hard work (physical activity) that benefit the world and they earn money. Today, I can buy a set of GPUs and let it run without me investing a lot of time on it (apart from initial setup) and still earn some bitcoins (at the expense of the planet and climate change). Isn't Bitcoin a dangerous thing?
First, you need to understand what money is:
Money is a certificate that tells that we, the society, owe something to you. If you have 100 bucks, it means you have provided a contribution to us that values 100 points, so we have created a central bank and emitted an amount of certificates equivalent to the sum of all social debts (that's the role of central banks). Then, we have created laws that force all people to accept that certificates in exchange for any contributions. Then, having this system, which guarantees a fair value of the certificates via the central bank and its validity via our laws, we give you a bill which values 100 bucks.
Now, you can use that money to buy anything you like. For your information, bitcoin is not a coin, but moreover a digital jewel.
We, the society, cannot tell what you use your 100 bucks on. You can buy beer or bitcoins that's up to you.
But since bitcoin doesn't fill the requirements to be considered money, and since bitcoin is a jewel, the equivalent of a valuable email stored on your Hotmail account, it changes value depending on the society. Values change, that's an essential economic fact. So, if you pay 100 bucks for 100 bitcoins, and then, society thinks that bitcoin is not valuable because a hacker found a flaw on the code, and 100 bitcoins get a value of 1 buck, you cannot blame nobody (specially us, the society) for your bad choice.
Bitcoin is not a risk per se. It allows speculation, which is like a lottery that pays the first ones. But most of the people buys such lottery and lose. If you want to speculate with economic assets, you must be very good and fast. On the other hand, the only ethical facet about the use of money does not regard money, but the owner. Bitcoin is as ethical as a rock. Some people pays big money for rocks or classical paintings. Van Gogh is not to be blamed for any unethical use of any of his paintings that worth millions. Is the contamination generated by bitcoin worse than the contamination generated by Stack Exchange? Should we shutdown both? We will not. We are just trying to survive using tools.
The only value of bitcoin is just being the first digital asset, which is technically false: you can Google for the million dollar web page, a student who sold pixels at 1 dollar each, earning a million dollars.
A bitcoin or a dot on the million dollars page are just subjective beliefs of worthy digital assets.