Let me just jump in here :D I believe that belief alone make's something real, because it does, on the astral plane, but enough belief can make it a psychical force (Karma, rule of 3)I believe demons, angels and the sort are either spirits, or just forces, that are there because we believe there there (note: doesn't make them any less dangerous)so if enough people believed in this "Demon prince" then i guess, it is real, but summoning it is bad because:
2) Demons don't like to leave when there told
3) Demons mess with your head
4) Demons make your life hell
Now some people work with demons and i am not trying to offend, this is just the likely outcome if you SUMMON a demon without just cause. What is your reason for this anyway, i don't think it will do anything just because it is told.