You know, when WoW first started, the Alliance was the "evil" faction. The Nobles of Stormwind were corrupted. The Night Elves were lead by a crazy Arch Druid. The Gnomes didn't really do anything and the Dwarves just wanted to kill every Dark Iron. During that time, the Horde was lead by Vol'Jin, Cairne and Thrall on Kalimdor, and all three of them are peaceful and don't rush to war. Sylvanas was really the only leader that wanted the faction war.
Now it's a bit switched with Varian back and cooled off. Thrall left and took over the Horde and his first act as a Warchief was kill Cairne. The roles actually switched with Alliance being the good guys and Horde acting like bad guys, although the Forsaken show a lot of redeeming qualities for themselves.