If this was truly the fear, we would see these types of people wearing masks religiously. But we don't, which means it's not a medical fear, it's a political one.
These are also the same people that won't get a flu vaccine, and resist getting the vaccines for all but the most deadly of diseases.
Another comment in this submission mentioned being bad at evaluating risk, perhaps that's what it is. They fixate on the unknowns of a vaccine, but they aren't able to compare it effectively to the risks of the virus.
This is not even remotely the common case. Overall, the overlap between anti-mask and anti-vaccination individuals is massive:
https://biomedicalodyssey.blogs.hopkinsmedicine.org/2020/09/...
The core of both is the same: anti-science and anti-society.