I have a very... different view on these things then most.  I have experienced an entity and this experienced eventually turned out "demonic" in nature and it was something I had to face.  Through this ordeal I went through an intuitive awakening, faced my own fears, and eliminated many weak points in myself.  At the end of the day i'm more sane now then I was 15 years ago, and in part this entity is to thank for that.  I don't see things as good or evil anymore but if I could describe what I experienced it one word it would be chaos.  I don't believe there's any higher order to these things due to their chaotic nature, therefore I doubt there is some agenda to destroy civilization by these entities.  To destroy order would create an inbalance, and fundamentally I don't believe it would be possible.  I think many people here give them power with their own belief systems, in many ways the reality we experience is effected by our beliefs.  My advice is to experience without expecting and make your own conclusions about it.  Besides, that is the path any philosopher would take so it should be good enough for you guys.... you are treading on shaky ground here.  You may invite yourself to experience something you definitely did not want too