Zynga is vile. But they're the good guys here, without argument. The idea that you can protect a game genre is nonsense, and terribly damaging. Imagine if Id sued Epic or Valve to kill Unreal and HL2? Imagine if Blizzard killed all the competing RTS? Imagine if Sony killed WoW?
This isn't about stealing from 'The Sims' franchise. It's stealing from the Facebook game, 'The Sims Social'. It's direct, not a matter of genre copyright.