I'm not talking about classic Bible thumpers. I'm referring to the upper middle class, lefty set as a non-traditional, special form of deity worship. The whole 'chemicals are bad' mentality is one that is based on fear, misunderstanding, and allegiance to a natural order that doesn't exist. I think anyone who sees a grand order in the world is a deist by nature (not that there's anything wrong with that), and that rejection of things that aren't 'natural' is a form of religious belief.
Those are the ones that I usually deal with. Mostly people that I met on "goa" type parties. They have many spiritual experiences, some of them have a hindu or sikh background etc. and they believe that it is not natural to put aluminium inside their children. Additionally, some say that they don't vaccinate because the weak viruses that are used in the vaccine are sometime acquired from animals that were treated with the virus. Which means that they are using "animal products". So vegans/vegetarians are against that. I don't have a problem with them being vegetarian or vegan or whatever. But when their choice starts to affect me or possibly my own children, then its not a choice anymore. Because with their "choice" they are putting other people at risk...