An ineffective message in this case might well have been worse than no message. Had the West attempted to intervene, either by setting up a no-fly zone or even sending in ground troops, and the killings not stopped, it would have sent a message that Western threats and Western power are a paper tiger.  Worse, if the genocide had reversed itself after Western intervention, the West would have found itself with both the moral and the political responsibility for the violence, and accusations of Western bias and even complicity would spread rapidly.