Why do people fear demons? I have no problem.?

the word Demon derives off of Daemon which means messenger. A demon is simply a entity from another realm or "dimension" if you like it that way. I know many people who have dealt with them and they cause no problem. Until you renig on theyre deals of course, not a smart thing to do. Not to mention they only come when welcomed. Explain to me why the bible says to steer clear? Not one of my friends are hurt or anything. Over dramatization?