I heard Dr. Haidt (sp?) say that while liberals mock conservatives for retaining traditional morality regarding sexual purity, liberals have that purity form of ethics, too, but increasingly about food.
Thus the demand for vegetarian/vegan, locally sourced, ethically raised everything - akin to Kosher but without the standardized rules and people adding more layers of exclusivity or perceived morality to try to outdo each other.
What's really meant by that is "without that yucky religious stuff". They are leftists after all.