Just to throw this in there regarding the forsaken. Perhaps the reason behind why the forsaken hate the alliance, and the humans in general, comes from two fronts.
One, because as its been discribed the forsaken hate humans because of how they were treated when they, having gained there free will, tried to return to there homes, there families, and they were regarded as monsters by the humans still living there, friends and family who they tried to turn to but were cast off as abominations.
Based from this, the other reason is, because of what humans regarded them as and how this rubbed off on the forsaken now with there free will, they began to see humans with a weakness and disdain, the same as what humans saw when they saw forsaken, the same disgust. As forsaken were human once themselves, the trait of simply disregarding what wasn't the same as them, but at the same time being a pale reflection of themselves, still remained as a reflection of there inner turmoil.
basicly, human ignorance still exists in the forsaken, and if humans themselves can be as ignorant to regard there once kin as monsters, why then should the forsaken be any different in how they regard them? Forsaken are corrupted humans at the end of it, and follow the same code of practice.