Ultimately they are victims of the system. They begin with a kernel of justified and understandable suspicion toward big corporate pharma but they build around that a whole edifice of paranoid conspiracy theories and unscientific bunk because they lack the dialectical materialist understanding to contextualize what is happening in the world around them. Like most people they instinctively feel that something is wrong and that the capitalist system does not serve their best interests, but not having (and not being allowed to have) a coherent systemic critique they resort to idealist fantasies and the blaming of individuals and secret cabals. Initially they harm themselves and those closest to them (especially their children) by refusing to vaccinate, but they do also harm society when their numbers grow to such a extent that almost eradicated diseases like measles start making a comeback.