There are two problems with demons:
1. Misunderstanding what good/evil is.
2. Ecology.
People dont understand morality. You get two types, basically. Absolute morality, usually your bible thumpers or karma reincarnators, and relative morality, which are your arrogant atheists and "True-Communism-Was-Never-Tried" socialists.
Let's be blunt. By definition, the concepts of Good and Evil are CONCEPTS, and all concepts are defined by the person using them, so good and evil is always subjective. Case closed. There is no real good and evil, right?
OH FUCK NO.
People seem to think that because 'I can change my point of view, therefore I can change what is good or evil' actually is a big brain idea. It isn't. You can change good and evil... FOR YOU. You can't change it for me, and you can't change it for society. You want to believe murdering puppies is "good"? Fine. You can do that.
YOU JUST CHECKED OUT OF SOCIETY.
Society has rules, you follow them, or society punishes you. You become the evil. Now, is this right? Is this fair? NO ONE CARES. Take your, 'I define reality' bullshit and get fucked. Raping your sister is bad. Society thinks it is bad. I'm with society on this one. If you want to believe this is good, guess what? Get the hell out of my society, you freak. You quit, the moment you decided to take this "evil" position.
Just because something is relative, doesn't make it WRONG.
You don't redefine good and evil, you redefine where you stand in comparison to everyone else.
SO, while demons might not think they are evil, because eating a human soul is perfectly fine to them, it also means that over here, in the human camp, they are fuckin' evil and all this 'they are just misunderstood" crap is just that. CRAP. You go feed your soul to the demon, I'll choose to think it's bad and stab him instead.
Which brings us to ecology.
Demons... are fiction.
YES. I KNOW. Big Brain ideas here, huh?
My point is, one must DEFINE the demon first and most people don't. Most story just has: Ooo, Demon! He has creepy powers! He eats Souls... somehow! The female demons are all sexy and shit and want to eat your soul through your dick.
Uhh... why? How? What is the goddamn REASON? Hell, the mechanism by which this happens? If I don't know this, your demons suck ass. They are a joke. If you define this, then I can tell you more about the demon's morality. If demons need souls to live, then, well, they aren't evil to THEM, but to us, they are evil. Like a bunny thinks a wolf is evil. I dont care about how the wolf feels. I"M A BUNNY. I'm on team bunny and Team wolf can fuckin' die when I nuke that wolf with a A-10 Warthog.
But what if, the demons just get POWER from humans? Like, they get mana to power their magic from human suffering? They feed off negative emotions. Well... Demons don't need to KILL humans, and humans suffer all the time, so I'm sure there is enough natural mama floating about. But if you want to supercharge yourself, you need to MAKE suffering.
Now only SOME demons are evil and some neutral. It'd be like if YOU had magical power, but you could bind a spirit into a rock and torture the rock to get more spells each day. Are YOU evil? (The answer is, YES, BTW) You don't NEED it. You WANT it. That is being selfish.
I would argue that the second type of demons are more evil than the first, because they have a CHOICE, but they are not INHERENTLY evil, like the first. The first, we cannot EVER get along. The second, we could, but it would take work.
Now you have another group which I alluded to before. The ALIEN MIND DEMON.
I hate BONES. BONES ARE EVIL. All humans must die because they have bones. I MENTALLY cannot understand bones. Like someone who freaks out over bed bugs and wants them all dead, I hate endoskeletons.
This is Blue-Orange morality. Not black and white. You have Good vrs Evil, I have Bacon vrs Bones. Bacon is my good. Bones are my evil. I, as an alien brain with alien thoughts simply think this way and I cannot UNDERSTAND any other way.
I don't land on your morality scale. I am perpendicular to Good/Evil or Law/Chaos. I am Bacon/Bones and what I do is perfectly logical from my point of view. Why? BECAUSE OF MY ECOLOGY. I am sure if you understood the alien dimension I came from, you would also understand why Bacon is good and Bones are bad. And for that reason, in your universe, I am confused as fuck. Why are you protecting your wife? Why does she scream as I help her be free from the tyrany of bones? Yes, she is dying, but seriously, you are better off dead then being filled with bones. Hold on, almost done. Just got to get this skull thingie, then I'll come help you.
"demon" is just a made up thing, so how to make the think is what's important.
I notice your choice of demons don't land on this scale anywhere.