This is one of the scary cards. There are cards in the deck that can frighten people, and often propagates the occult-ish "evil" reputation tarot has, especially among certain religious views. Even if you understand that Tarot and the cards are really about ideas and learning (not predictions and superstitions), even then, the artwork on some of the cards can be a little on the dark and disturbing side...like the guy face down with swords stuck in him on the Rider-Waite 10 of swords. Death and the Devil aren't exactly cheerful-looking, no matter which deck you use.
These cards are part of the Tarot deck for a reason far more intimidating than satanism or witchcraft...they are there because of reality.
While we might not enjoy thinking about it, the reality is that we all die. The reality is that there really is violence and injustice in the world. There is a dark side to life on planet Earth, and yes, fear and anger can take you there.
When the Devil card turns up in a reading, it isn't a prediction that something terrible is about to happen to you. That's an easy prediction to make, because we all experience ups and downs and bumps in the road - some bigger than others.
When this card turns up, there is nothing wrong with taking precautions...forewarned is fore-armed. The problem comes when practical caution turns into fear and paranoia. I like to re-frame this card as a "use your street smarts" card. Think of it as a crook, gangster, drug dealer kind of card to put it into perspective.
The Devil card is a reminder that injustice and wrongdoing really does exist, and asks us to think about what we are going to do about that incontrovertible and unavoidable fact.
"The Devil", injustice, and "evil" are part of the wholeness of everything. That doesn't mean we have to accept them. While it takes some work, we can find some tiny measure good in evil when lessons are learned from tragedy. Wrong is in the world for a right reason...to teach us how to protect against it.
Injustice is in the world to teach us how to fight and overcome it.
It is a card that can bring out the fear in us, or it can bring out the ethical warrior in us. The choice is, as always, yours.