Even though not very much implemented and badly supported, the RP aspect of WoW exists. As such, the question must be asked - who are the “bad guys” of WoW?
Trolls, once cannibalistic and brutal, overcame their dietary habits and Vodoo practices to become a Shamanistic and loyal partner to the Horde. Orcs, the abused race whose homeland of Draenor was invaded first by Draenei and later by Sargeras on his pursuit of the Draenei, were first enslaved, then forced to act against their own peaceful and shamanistic ways, later imprisoned by Humans and only freed when Thrall rose from the shackles of the Orcish past. Tauren, another peaceful and nomadic people, plagued by Centaur invasions into their stomping grounds apparently had little to no help from Humans, Night Elves, Dwarves, or Gnomes. In their pain, Thrall came to help, and Cairne Bloodhoof built the Tauren’s first fortfied city above Thunder Bluff. Lastly, the Undead. Now, here we have some true opportunism, allegiance due to convenience, and a clear threat of Undercity breaking from the Horde as soon as the Dark Lady’s dark motives are met.
Blood Elves, likewise, aren’t that much of an open book to read. Seeking Magic like a Meth addict a dealer, there is no knowing how far this new ally will go to obtain their Precious.
Humans - advised by a Dragon, sister of Nefarian, and blinded by The Light as much as either ignorant or ambivalent to the dangers of Onyxia, the plight of their native neighbors, the Tauren, picked an alliance with Night Elves, Gnomes, and Dwarves.
Gnomes, exiles of Gnomeregan, infatuated by the might of what would be a planned super-technology center, allowed the radiation to give rise to the Mutant Troggs. Ever the inventors, High Tinker Mekkatorque and his men turned a whole city into one big nuke in an attempt to stem the invasion. Turns out that one didn’t quite work, giving us more infested Troggs all over Azeroth, a green glowing former city, run by the traitor Mekkiner Thermaplugg, and a reason not to trust Gnomes with technology.
Dwarves, a down to earth people, are maybe the true victims of this Alliance. Convinced to be the descendents of the mighty Titans, Dwarves seek nothing more than their own heritage. In this pursuit, mistakes were made that contributed to the expansion of the Burning Legion and powerhold of Sargeras, that might ultimately have destroyed any hope of knowing for sure about the where and when.
Lastly, Night Elves. If there is such a thing as “THE” perpetrator of the Burning Crusade’s deadly reign in Azeroth, it would be the Night Elves lust for power, egomania, and elitism. It was Azshara and Xavius who opened the Dark Portal, lured by Sargeras’ promises to eradicate “unworthy” races from Azeroth. The Highborne, Elves born into nobility, hoped to reap the fruits of what they perceived as their true calling, rulership over and cleansing of Azeroth.
The Draenei fell almost completely for the lure offered by Sargeras. Only a few survived uncorrupted, fleeing from Sargeras across the Universe onto Outland where their presence unltimately doomed the peace loving Orcs which were completely unaware of the danger, unprepared to fight it, and unable to withstand the corruption.
Who are the good guys? Neither Horde nor Alliance are free of past guilt, having doomed whole planets, given power to the Red Dragonflight, turned a city into a nuke, eaten their own, or scheming to develop a new Plague. Is there such a thing as playing a good guy?