An interesting related recent post from Haidt regards the similarity between the social conservative attitude to sexual purity/sanctity and the left liberal attitude to food and the environment:

Yet there are enough hints of “liberal purity” scattered about that we at Yourmorals are actively trying to measure it ... It can be seen in the liberal tendency to moralize food and eating, beyond its nutritive/material aspects. (See this fabulous essay by Mary Eberstadt comparing the way the left moralizes food and the right moralizes sex). It can be seen in the way the left treats environmental issues and the natural world as something sacred, to be cared for above and beyond its consequences for human – or even animal—welfare.