Prior to the Iraq War, the war in Libya, and any intervention we may or may not undertake in Syria, some hawks insistently argue(d) that there is a humanitarian imperative to step into the breach.
Their arguments can be powerful.
Innocent people are dying at the hands of a tyrant. We have the most powerful military on earth. If we do nothing, the slaughter will continue. And don't most of us agree that some military interventions, like the one that stopped the Holocaust, would've been justified on purely humanitarian grounds, even if stopping the death camps wasn't the rationale for WWII at the time?
There are many non-interventionist counterarguments. One is that even in situations where death is guaranteed absent intervention, it is still possible to unwittingly make a terrible situation worse.
Another is that war is very costly in U.S. lives and treasure.
And isn't it unfair to order people who joined the military to defend their country to risk their lives for a different cause, however noble?
While open to interventions in the most extreme cases, I'm generally a non-interventionist, and although there are several reasons I feel that way, one in particular seems to be missing from the national debate: Almost every time someone calls for a war to be entered on humanitarian grounds, there's a way to save more lives more cheaply and reliably with philanthropic spending.
~ from The Flaw in Many Humanitarian Arguments for War by Conor Friedersdorf ~
Let me add my own counterargument: If the US genuinely promoted peace, justice and human rights in our foreign policy -- as well as within our own borders -- a lot of these situations wouldn't develop in the first place. Most of the nations that receive our interventions are those in which we have spent numerous years propping up their dictators. As long as these thugs do our bidding and/or allow us to steal their citizens' natural resources, we overlook their despotic tendencies and hold them close to our bosom. Consequently, the support of our elites often is a precipitating cause of unrest among their own people.
Rather than ramming "democracy" down people's throat with the barrel of a gun, I think we could do a lot more good if we modeled real democracy in the way our nation conducts itself in all it does. Like the old saying goes, an ounce of prevention is worth a pound of cure!