I would say, please read the books They explain A lot.
For example: Sylvanas has plenty of reasons of Hating everyone. Her soul was litteraly ripped from her body and she got turned into a banshee after getting frostmourne stabbed straight through her chest, and this was because of the Human Prince Arthas.
The blood elves are not magic addicts, they are simply trying to survive and it was Kael'Thas who went mad, not the Blood elves as a people, ever since getting back the Sunwell they have managed to control their addiction.
Orcs, plenty of reasons to feel sorry for them, they got turned against their peaceful allies the Draenei just because Gul'Dan, apprentice of Ner'Zul was too hungry for power so he sold his people into demon slavery, much like how the Demon races were enslaved.
Goblins are not really based on lore, more based on Gameplay.
Id cover all aspects of the horde but considering im Still at work I think this will suffice as a starter
Kindest Regards
//Naz