In the final commission before Jesus went back to sit on the right hand of the Father in heaven, HIs last instructions were to deliver people who are possessed of devils.
He did not infer in any way that these devils could hurt believers or could even stand up against them. He told His disciples to cast them out!
The Word of God is either true or not true. If we as Christians have authority to cast out demons, we must obey. "Casting out" is an offensive action. This means to take the initiative and be the aggressor.