Good question , and this is the same question I used to ask myself. Several years ago, I was given a photo by a monk whom I do not know while I was in a shopping mall one day, When I first saw the photo, I took an immediate fondness to the image I saw. I kept it in my purse and it went everywhere with me and would often take it out to 'talk to him' whenever I feel disturbed by a situation in office. He seems to be providing me with answers to my issues at work.
One day one of my colleague saw it and told me that he is a demon. I was very hurt as he has been my friend and ally. Unfortunately, I could not defend because I did not have much access to information about him until I found dorjeshugden.com.
I think I must have prayed to him in my previous lives for me to take an immediate liking to him. It is affinity. Even if someone does not read or know his history/background, and looking at myself today, He could not possibly be anything except an enlightened being. You see, I am an able and healthy human being with strong inclination towards Buddhism. If he is a demon and I had been praying to him in my past lives, I think I will still be in hell now and not typing this on your forum. My analogy based on a simplistic mind.