> A good example of this is [...] anti vaxxers. They've got no scientific or reasonable leg to stand on

You should read up on the Leicester Method.

I have no opinion one way or the other, but it seems to me, that rather than malleable minds being "influenced" by propaganda, it is a natural reaction to being "told" what to think.

Pro vaccine advocates, come across much the same as modern atheists, or rust users - vehemently proselytising their views, with little regard to the fears, concerns, or opinions of others. This naturally rubs people the wrong way, especially if one is predisposed to contrarianism.