Came here to say the same thing. It is pretty ironic that in an essay that is basically criticizing people who can’t put up with heretics, he is doing the same thing with regards to "anti-vaxxers" without even realizing it. It doesn’t help that the term specifically (according to Merriam-Webster) is defined as:
> a person who opposes the use of vaccines or regulations mandating vaccination
It is a loaded term that is used mostly as a means to vilify people. There must be a lot of people who are pro vaccine, but against government mandates, so where does that leave them? Also, it is possible to be generally pro vaccines, but also skeptical of new vaccine technologies rushed through development and regulatory approvals in record time where the companies leading the push have a history of putting profits ahead of public health.
The fact that your comment shows up in gray here is further proof of the exact dynamic that he is referring to in the essay:
> But occasionally, like a vector field whose elements become aligned, a large number of aggressively conventional-minded people unite behind some ideology all at once. Then they become much more of a problem, because a mob dynamic takes over, where the enthusiasm of each participant is increased by the enthusiasm of the others.