Once again:
The cost of producing hashs is not a short term cost. It requires a long term investment in the hardware that produces them, so unless there's a way to double spend for hundreds of blocks without crashing the value of bitcoins, it would not be worth it. It would be more lucrative to just be honest.
Proponents of bitcoin have trouble grasping the fact that "evil empire" won't care about the lucrativity. Bitcoin is powered by fiat and probably always will be, there is almost no way to separate the two unless electric companies start taking bitcoins as payment. If someone wants to mess with bitcoin purely to mess with it, the resources required are far from insurmountable. Crashing bitcoin would be the endgame, not a side effect.