Refers to the wave of hippies in the late 1960s and early 1970s who migrated to born-again evangelical Christianity. This may seem like an odd choice for hippies on the surface, but not so much really: it provided a model of communal living, a mystical worldview in which the spirit realm is always present in one's life, and a transformation of their existing secular Us vs. Them stance into a cosmic struggle between primal Good and primal Evil.
Originally opposed to the Man as represented by secular institutions like the United States government, they found another opponent in the mainstream churches who were initially deeply suspicious of these long-haired weirdos who started showing up at their services.