I think the term "racism" gets severely overused, and this thread seems to bear that out.
Outside of WoW, I am perfectly within my rights to like or dislike anybody I want, as long as I don't infringe on their rights by doing so.
In WoW, there is no such necessity of holding back the dislike. The humans hold a deep-seated hatred of orcs ever since the first time they laid seige to Stormwind. Yes, the current horde isn't the same orcs that attacked Stormwind, but they are orcs nonetheless. When Thrall was in charge it may have been ok to talk about peace because that's the kind of leader Thrall was. Now with Garrosh in charge, peace is the last thing the Horde wants to discuss.
Varian as a leader isn't much better. I'm not entirely sure why, but he is hell-bent on erasing any of the peace that had been established between the Horde and Alliance while he was benig held captive. I'm not saying he's as bloodthirsty as Garrosh, but he certainly won't back down from a fight, especially one he thinks he can win.
And Idiggory, if "these bastards want to kill me" isn't enough motivation for you to take part in the conlict, then I don't know what is.
As for me, I'll be on my rogue, ganking hordies whenever possible.