It's worth remembering that the event that, uh, kickstarted their drive for unionization was the site's management banning a project that was raising money to support violence against conservatives (the actual physical kind, not words). The details are a bit fuzzy now but iirc some of the hard-left employees didn't like the ToS being enforced in that case, because whilst they accepted the project was calling for violence they felt that encouraging people to "punch Nazis" should explicitly be allowed. They felt that strongly enough that they unionized to force management to acquiesce.
So this isn't a classical union that's requesting more money for the workers or anything. It's the new sort of union which tries to force companies to take sides in the culture war.
It's thus not a surprise that a significant proportion of workers wouldn't want to be a part of that, and well, the sort of people who were unionizing the firm were doing so explicitly to support physical violence. US unions have a long history of violence already.
https://www.washingtonpost.com/business/2019/10/10/how-debat...