I think I'd place that bar based on likely success. There are plenty of dictators doing awful enough things in countries where we simply could not do what we did in Iraq. Mugabe, for example, is pretty popular with a big portion of his citizens, in no small part because he's sticking it to the colonial leftovers; a bunch more white guys with guns marching into the country is not a solution. Thus, the moral case against a dictator is not the same as the moral responsibility to take a certain course of action. Perhaps this is nowhere clearer than North Korea (I told you I'd address this sooner or later!), where nuclear weapons are the great complication. Incinerated Koreans will have a hard time exercising the natural rights we want to bring them, so an outright invasion is hard to justify. Nevertheless, I don't find anything wrongheaded or "cowboyish" in a policy of outright confrontation toward Dear Leader, a stated goal of regime change, and the willingness, however horrible it may be to contemplate, to let him starve his own people in order to pursue weapons. It sure beats another empty treaty by which we feed and heat his country, in effect subsidizing his military ambitions.