Sliding Scale Ethics

When challenged with an "ends justifying the means" debate we often go to the extreme cases of survival, revenge, war, and life or death decisions. I suspect that we strain our capacity to think critically while our "fight or flight instinct" is in full gear. Certainly Pearl Harbor, The extermination camps, The bombing of Hiroshima and the World Trade Center are incidents that strain our ethical framework to the limit. The wealth generated by Blackwater in the wake of 9/11 certainly exemplifies this point. It makes me wonder if there is a scale upon which this question is judged? If I invade the Middle East in response to 9/11 is that Justified even if I would never cut in line at the supermarket in front of an old lady so I could get my cheese sandwich faster which, after all, will raise my blood sugar and allow me to be more effective at my church fund-raiser?