> I only want to belong to a social network that values science and public health. Why shouldn't I be allowed to be a user of a website that has those same values?

I think it's a problem of expectations.

Some expect Facebook to just be a social network. Others, like you, expect it to be a safe space where unapproved opinions aren't allowed. Neither kind is bad per se, but I don't think most people expected Facebook to be of the latter kind.