I'm grabbing popcorn for this one ...
(Not to be one of those people who comments but doesn't offer help, if it were me I'd replace the entire base. One possible suggestion - find a different base second hand and adapt it to fit the chair. There is no karmic rule that says the base has to be the same brand as the chair, or even match it. It all depends on how the existing chair attaches. You might even take the modifications to an extreme).
But anti-vax misinformation , which literally kills people, is perfectly fine.
This guy likes to portray himself as a rationalist and a free thinker, but he is nothing more than a scared man-child willing to pander to the dregs of society just for $8 and a dose of validation.
The sooner this festering boil of a social media site implodes, the better.