Angels! ?
Well, this'll be interesting. The standard trope when you already have 'decent demons and humans understanding' is;
"Angels are 'good', but in such a stubborn way that their version of good means murdering all that they _presume_ to be evil." (e.g. 'all demons' and 'humans that aid demons').
Basically the same as that order of holy knights, which just kill all demons on sight. At the point where you're just causing massacres, you might as well be evil. Let's see if these angels fall outside of the trope and actually think about things.