They don't want anybody around with the sight. If you have the gift and can see the demons, you can also kill them, very easily. Swear allegiance to the almighty and avoid sin and do his rituals, and you become a spiritual juggernaut. His good favor will make you glow with a golden light that burns hotter than the sun to demons. Witches hate people like that because they are born with a gift of sight that they themselves have to sell their souls to obtain, and they only ever get a cheap knockoff of the real deal in return, and when one of the truly gifted and blessed walks into the room, the witches are forced to close their third eye from the brilliance of the aura. When you submit fully to the almighty, your true power as a Son or Daughter of Adam awakens and you can crush Lucifer himself like a bug if he ever shows himself to you.