The underlying technology of cryptocurrency is based on a world without trust. Its most ardent proponents want to demolish institutions and abolish regulation, reducing the world to a numbers game which they believe they can win. If the wildest fantasies of cryptocurrency enthusiasts were to come true, if all the environmental and technical objections were to fall away, the result would be financial capitalism with all the brakes taken off.
The promotion of cryptocurrencies is at best irresponsible, an advertisement for an unregulated casino. At worst it is an environmental disaster, a predatory pyramid scheme, and a commitment to an ideology of greed and distrust. I believe the only ethical response is to reject it in all its forms.