The Order of Nine Angles is a group of devil-worshippers, not Satanists. They are a cult. From the wikipedia entry about them:
The ONA's writings condone and encourage human sacrifice[10][11][12][13] as a means of eliminating the weak: Anton Long describes it as "a contribution to improving the human stock, removing the worthless, the weak, the diseased (in terms of character)".[14] This "culling" serves not just a Darwinian purpose, but is also connected to the promotion of a new Aeon: "The change that is necessary means that there must be a culling, or many cullings, which remove the worthless and those detrimental to further evolution."[15] Thus, true Satanism, they assert, requires venturing into the realm of the forbidden and illegal, in order to make contact with the "sphere of acausal, sinister forces on the cosmos."