Yes, there are people in this world who are actually demonic themselves, nevertheless, the devil often uses or works through negative people in order to distract us or to cause conflict and confusion.
The devil will even manifest in people who claim to be Christian or followers of God.
When we are of the light attacks will always come against us yet we have authority over evil and are equipped for the challenges.
Remember, the Lord fights our battles, and when we come up against those who are tools for the devil we are not affected.
The darkness can never overpower the light as I have said so many times before.