Most people who have a religion believe that their religion is true, not merely a matter of interpretation. So "according to his religion" = "the truth, in his opinion".
For the record, I believe that Wicca is entirely man-made, and Satan probably has no influence over it at all. There's really nothing Satanic about it; the themes don't match. In order for something to be Satanic, it would have to be based on selfishness and egoism as the supreme values.
So, you know, something like Ayn Rand's views. Now that is Satanic.