Because your definition of evil is not consistent with Christian history or theology. That is the relevance.
The concept of evil is actually Jewish, not Christian and it is equated with sin, bibically.
The modern sociological and philosophical concept of evil is quite different from what you've described, and all Christians I've known my whole life who I've discussed this with do not use it as you and the others on this thread do.
You're free to believe as you wish, but understand that you do not speak for all Christians even though you say you do.