So can narcissism
. (Sorry private inside joke).
But we live and learn and come out wiser.
Anyway, god, I thought the same, I was brought up indoctirinated*
, and its normal to fear all this, like demons are evil case closed, and possession is an evil takeover lol, until, no other way, but by getting to know them personally, (and unfortunately being annoyingly untrusting in the beggining), through experience and trying, asking the questions…, inched my fear and trusted them. Start small test the waters. No rush for the process… Now Im a believer
. Perferably, from my experience, dont let anyone tell you what it is and is not, get to know them, test the waters, and then you wont need any more conformation than your own experience. And from my experience, in short, no, demons are not ‘evil’. Im not saying that there arnt ‘bad’ spirits out there… and there are general respect that has to be shown. Stick to the Goatia ones you wont go far wrong, and see who you work better with, but note, drop all perceptions of what has been onced told or pictures from grimiors even what to expect and their ‘charactaristics’. Invoke, find out and see. From there build a relationship and from there you are in charge what feels comfortable and try maybe gradually while working together with their support. You might slowly find out what you have been duped and actually what resonates. If you choose to go down this path, I wish you good luck 
It reminds me abit of intimacy and boundaries and social ettiqet. If you trust the person enough to have intimacy (possession) than take it slow if you will and your partner (demon) would understand, and even work with you through it … and not rely soly from books… Its ok to be weary at this stage, especially from fears of past indoctirination. But if this path is calling you, and if you choose, slowly all will be revealed. Another thing I learnt on my journey, never put your abilities down just because you feel you dont know everything, your spirituality flows through you and is part of your human birthright, however big or small to start, it just depends how much one is willing to exercise that, and your individual protection and connection trust in that, however much you seem to know or not just yet, especially around the ‘big boy’ magicians dont let them put you down, but be open to greatfully learning. There is always more.