When a person denies his conscience for too long, it can become seared. That person becomes susceptible to receiving and accepting all sorts of harmful and evil things. This is true for both believers and unbelievers. A seared conscience will open a person up to demonic spirits and activities.
Henry Hon, ONE: Unfolding God's Eternal Purpose from House to House
clear-conscience, conscience, demons, evil, evil-spirits, good-conscience, shootings, why, why-is-there-evil