If the U.S moves to prevent some country from slaughtering their neighbors, then "world opinion" says we are interfering with their devine right to slaughter their neighbors. In Iraq the "no fly zone" unjustly interferes with Sadam's devine right to slaughter Kurds - how very bad of us.
If we stand by and do nothing, then "world opinion" acuses us of doing nothing as thousands are slaughtered.
No matter what we do "world opinion" says we are wrong, so we have to do what we feel is the best we can do under the circumstances and "world opinion" can suck rocks.