You misunderstand the meaning of volunteer in this context. It does not mean that the reason to run a full node is for "the greater benefit of society from the goodness of their hearts" (though the cost of running a Bitcoin full node is minuscule enough that many may do so according to those reasons), no - it means that full nodes are run unpaid for the good of the Bitcoin network; its actually crucial to the argument of the piece which your emotions distracted you from addressing.
But first your basic conception of Bitcoin will be addressed, since its all you opined on (why even respond if you aren't addressing the article?)
If Bitcoin only served miners it would not be around. Miners are paid indirectly by the rising price in Bitcoin, so those purchasing it are the ones who are setting that value - they are fully consenting to the simple and genius system for its economic and technological properties which they cannot get anywhere else. The Bitcoin system is very simple; if it was purely extractive as you claim people would not use it as a store of value and transaction layer. Considering large portions of users hold their coins through large price action, and have done so for the entire duration of its lifetime, they consider it useful beyond speculation. Who are you to tell them they are wrong in so few words? And if an invention is deemed valuable, why shouldn't it use energy?
And we haven't even gotten to the article yet, because you misunderstood the economic context for your preconception of a vocal subset of a community that the author is in disagreement with.