If artists don’t want their data, their art being scraped by giant machines without any human oversight for profit they should be within their right to opt out. If they cannot opt out, why not poison the ill-gotten gains.
If the corporations behind these Machine Learning Algorithms were altruistic or open source, like Wikipedia is, perhaps I’d see your point. But not wanting your art to be sucked into a black hole to then be sold to others without credit or compensation I find more than fair.