You'd be surprised. Satanist actually have a code of morality of their own, which doesn't paint of picture of wanton horrific acts. They'll indulge in immoral pleasure, under consensual agreement no different than the world. In general human beings want a sense of peace and go about the day without duress or a sense of peril is on the horizon. Satanist even though they don't glorify God, are no different. There is an order lawfulness in their code, which has some overlap with Christianity, but the huge difference is who gets the glory and who gets to be God and who get recognized for setting up that code of behavior.
What this is, this pastor, is people being people and doing the natural. The natural of following their human nature run amok without God's moral code putting their decisions and behavior in check. At one time this pastor likely believed that harming children was unthinkable, but there came a point in time where sin in his life gave way to more sin and escalated his sinful wants via his human nature. He either probably justifies what he's doing in some contorted way, that God's got his back or he realizes what he is doing is wrong, hates himself for doing it, but the sin in his life is out of control, and feels helpless to stop it. Maybe having been caught will give him a sense of peace. He'll be forced to stop. Pay for his crimes. Get right with God.