You have pointed out an important distinction, and in the process explained the false equivalence between right and left on this issue.

In the internet age, there is no cause so deviant that you can't find a community of like-minded people, even something as despicable as resisting the duty to take simple measures to stop a plague. When you combine group identification (bolstered by politics and religion) with the intoxication of moral outrage, it's easy to see why the anti-vaxxers and anti-maskers are so hard to educate.