My advice is that you forget all that demon stuff, the world is crazier than you think, with ideas of sorts spinning left right center. I don't know but psychologists believe that people who see demons have a predisposed fear and respect for demons. To me if you are obsesses with anything that thing is your demon, sort of like endless hours of reading or playing PS2. I personally don't believe in Gods because there are just too many to choose from, I'd rather not follow any than to offend another, besides the whole idea just sounds too creepy. The number 1 doesn't really exist but its use makes it withstanding, thats the way most things work-Utility. Take out the utility and you will be fine, my guess is that your friend is a devout christian follower who believes in good and evil. Take your mate to an excorcist or call John constantine, if all else fails take him to the psychotic clinic.