One of the reasons that I find Noam Chomsky's point of view very persuasive is his ability to get to the heart of questions such as this. Chomsky by profession is a Professor of linguistics, linguistic theory, syntax, semantics and philosophy of language.
The reason I believe this is pertinant is that when you're dealing with heavily emotive scenarios such as the one you propose, semantics is everything. One man's abuse is another man's torture. Witness:
From a western point of view: The Iraqis tortue family man Nick Berg. A rogue element, which in no way indicated systemic failure, were responsible for abuse of Iraqi prisoners.
From an Iraqi point of view: The Infidel Godless Americans reaped what they sowed when a greedy American contractor, come to rape Iraq of its resources was executed in response to the Infidel Americans brutally torture innocent Iraqi citizens, may Allah have mercy on their souls.
So, Chomsky's solution is to say that you have to apply the same standards accross the board. That way, if you find something to be intolerable if it were done to you, it therefore becomes an intolerable thing to do to someone else. Until you can get to this point of view, it's almost depressingly inevitable that one set of people will justify their evil actions by contrasting them with those of another set of people.
More simply, Nick Berg & Mai Lai were both deplorable acts of gross evil. To try and make one more deplorable than another simply puts you back on an escallation footing.