The discussions range from whether 'the end justifies the means' to whether 'morally defensible acts should always apply without exception'. ie I can kill if it justifies the end result vs if killing is wrong I should never do it. Defending the end justifies the means is to defend Hitler's approach to total war, nuclear exchange, chemical and biological warfare and of course targeting civilians. Defending moral relativism (it is acceptable to kill in some circumstances) opens up an anti-religious standpoint (killing is wrong) and leaves room for interpretation by the individual (My Lai anyone?) Once you move down the relativism road then you must accept that one person's truth may be different from another's, after all it's all relative.
It's not a simple problem.