I think the writer means “a Satanist group.” The use of the pure adjectival form seems to imply a prejudicial moral judgement. For all we know, the Oklahoma Satanists are perfectly delightful people who love their children, pay their bills on time, and help old goats across the street.
Or is a Satanist satanic by definition? Perhaps the writer is a Satanist, and is gently pointing out a tragic ecumenical misunderstanding? Perhaps the hidden truth is that being satanic, never mind Satanist, is a warm, cuddly, utterly inoffensive and tragically misunderstood kind of business?
I admit to some confusion – and ever since reading Paradise Lost I have suspected that we underestimate God’s PR department.