In the spiritual world, evil spirits are in complete subjection to the angels of heaven. This is because the Lord made the statement that all power has been given to Him in heaven and upon the earth. The Lord governs everything in all of creation, both spiritual and natural. Nothing occurs that is outside of the Lord's Divine Providence. Quite often people have asked why evil people are successful in their desires if the Lord does govern all things, even in its minutest detail.
History is full of terrible acts of violence towards human beings.
The Holocaust, the Oklahoma City Bombing, and the recent shootings in Colorado are just a few acts where evil intentions have caused a tremendous amount of grief on the part of those who are innocent. One explanation the Writings for the New Church give is that when evil is permitted to express itself, mankind can take action to correct these acts of violence and seek to control them. Also, we have evidence of the destruction that evil brings. This can provide us with the incentive to address these evils so everyone can be protected as much as possible. They also can remind us that if our natural inclinations toward evil were not held in bounds, we would inflict an unimaginable amount of harm upon ourselves.