You’re missing the obvious.
Their power (short of unconstitutional brute force) is “proof by intimidation”.
Acting like the serious, sane, sober, mature, responsible, EDUCATED adults, with all the associated slanders.
All you have to do is to get one or other people to start snickering, and the Karens lose all their scold power.
So saying “let me put this prick in you or you get fired” works; it’s different enough that it suspends the spell while people puzzle it out; then when they do, they can’t help but grin at the joke; and the panic-induced blindness goes away.
And one of the reasons I answered that is that he specifically asked "legal minds", I'm a lawyer, so I gave him the legal explanation for why his argument was wrong.
Other arguments about why the vaccine mandate is illegal have nothing to do with my post.