As long as Christians waste their time and energy disagreeing and arguing among ourselves, we pose no threat to Satan. The surest way to stop fighting Satan is to fight among ourselves. A second tactic that Satan loves to use among Christians is selfishness. God placed an enormous emphasis in Israel and among Christians on the necessity of God's people existing as an unselfish community. For Satan, selfishness is a versatile weapon that is powerfully destructive in any situation.
Selfishness comes in many forms and is often hard to recognize.
Religion for religion's sake neither scares nor worries Satan. He doesn't care how many people attend a worship assembly. Bodies sitting on pews do not worry Satan. But hearts and minds that humbly worship God terrify him. He doesn't care how many members we have.