Pfizer has begun the process that will in a few weeks result in full, not Emergency Use, approval. Moderna will probably begin that process soon. So "experimental" will soon be incorrect for both vaccines.
So, the
... the DU-member's niece is a legal adult, and was living in her parents' house. Their house, their rules. I'm far from an anti-vaxxer, and having received both Pfizer doses, not vaccine hesitant. That said, the parents' house, the parents' rules. However foolish the DU-member may think the parents' action of throwing out their daughter, he should have limited his actions to asisisting the daughter. I suspect that both the daughter and the DU-member contributed a great deal of foolishness that escalated the situation to the daughter getting kicked out and the confrontation at the DU member's house. Assuming all that happened, of course.
How plausible? Hard-core anti-vaxxers have some real crazies among them. They seriously believe, variously: that mRNA vaccines reprogam recipients' DNA; vaccines actually make recipients more likely to get Covid; that recipients shed Covid viruses; that recipients shed dangerous virus spikes. I don't cruise anti-vax sites for their latest stupidity, those are all claims I've seen posted on conservative discussion sites, and I've probably forgotten a couple. So it is possible that the parents are really that kind of crazy, though a DUmmies would probably regard someone vaccine hesitant to be an anti-vaxxer. As for the extreme reactions, DUmmies amply demonstrate what anger, hatred, and fear can do.