They have to say NFTs/cryptocurrencies are destroying the planet. Because otherwise you can say stuff like "if you don't like NFTs, then just don't participate in them? Why do you care what other people do if it doesn't hurt you?"
Everyone agrees that violence is bad and should be banned, barring self-defense (though some are rethinking this post-Rittenhouse), so their goal is to stretch everything into literal violence. NFTs require energy, all forms of energy usage destroy the planet (since there's no form of energy production that exists, that they support, that creates enough cost-free energy to supply the world), destroying the planet is violence against everyone on it. Therefore, participating in NFTs is violence and needs to be banned.
Same reason anything they don't like (including supporting trans rights in an insufficient manner) can be "transphobic" and transphobia is literal violence genociding troons. Or how the rule of law is "white supremacy" upheld by violence. Or capitalism is. Or whatever else they want and want NOW. It's all the same shit to this cult. It's like they read (not really, reading is fascist)
Repressive Tolerance once and have formed an entire ideology based on implementing it. (Marcuse was serious, it's not Swiftian. Also, I'm not saying Marcuse invented this or is to blame, just that he wrote the most direct case for the principle.)