Undead are also fairly evil. They have basically genocidal ambitions, though maybe that's changed in the periods I've been away from the game.
Sort of. A Forsaken splintergroup betrayed Horde and Alliance during the first major battle against the Scourge at the Wrathgate, unleashing a deadly blight. Said Splintergroup was led by the demon who stood beside Sylvanas all the time in Undercity. He threw Sylvanas out and as a player you then had to fight your way through Undercity alongside Thrall and Sylvanas to reclaim it.
Ever since then, Thrall has replaced most of the Undercity guards with loyal Korkron guards. Sylvanas and the apothecaries got Orc supervisors too in order to keep a close eye on them.
If they're still planning genocide, it's gotten a lot more difficult with Thrall basically watching every move.