It has been proven time and time again that Humans in WoW are racists. From Garithos disrespecting the Blood Evles and causing them to join the Horde, to nearly every Human leader having a false sense of superiority over every different race around him/her. Truth be told, the Alliance would be nowhere without the high/blood elves, there would be no Jaina Proudmoore and there would be no Alliance because the Horde would have wiped them out. Because without the elves teaching them magic, they would just be Orcs except with less brainpower, strength, and green skin.