The thing is I think in-world the explanations for spirits and demons are deliberately dichotomous because most people want easy answers for things that are not so black and white. Solas tried to explain it even back in inquisition. (Thoughts about spirits and Spite under cut, sorry I get wordy)
Emotions are messy and nebulous, but people separate them into good and bad anyway because they don’t want to think about how they’re actually neutral. The actions you take because of these emotions can be used for good or to harm, but the emotions themselves are just natural responses to the world.
Spirits are entities that embody emotions, so if people believe there are good and bad emotions, that means there are good and bad spirits. They call these bad spirits demons, but in reality demons are just spirits reacting to emotions in ways that are often harmful. This can take many forms which means some demons will be very dangerous and some might be just a little mercurial. There are no hard and fast rules that just because a spirit can be considered a demon that means they have to cross a certain threshold of bad behavior.
We’re conditioned to think of spirits and demons as two separate things or at least two sides of a coin because we learn everything we know about them through very biased rhetoric. We start the story in southern Thedas which is very wary of magic and the fade. Even in the North they aren’t much bigger fans of “demons”.
But the thing is emotions are not only nebulous and hard to understand, they are also fluid. They change often and sometimes drastically. That’s why spirits are so easily influenced and ‘corrupted’ by outside variables.
Just like you can be a little annoyed or consumed with rage, or a bit upset or so depressed you can’t get out of bed, I don’t think all demons embodying negative emotions are equally dangerous. That’s why I dont necessarily agree with people who think it shouldn’t have been so easy to reason with Spite. Or that he should have been more volatile and dangerous.
Just like when you’re angry there are things you can do to calm down, when people (namely Lucanis and Rook) begin to listen to what he is saying and making an effort to understand him, Spite mellows out. He never really gave off the energy of the Rage or Pride demons you can fight as mini-bosses, but he calms even more because there’s less to fuel his negative emotion. I don’t think he ever stopped being a spirit of determination or passion or whatever he truly was before, it’s just that under duress emotions like that can evolve into more negative outlets even if at their core the emotions are the same.
I think most spirits are as much demons as they are spirits because I truly believe the only thing that changes is how they express themselves and their corresponding emotion. Thanks for coming to my ted talk.