What about all the innocent Iraqis and Afghanis the U.S. army has killed in the heat of war? Why don't we hear about them? Are they any less significant than British, American or Canadian innocents?
This is a tragedy and you can't discount what's happened here, not at all. But these journalists also assume a certain amount of risk when going in to the middle of a warzone to take pictures and cover a story. Maybe Reuters is to blame for not cautioning the American army about where their journalists are stationed? Who knows. Would the Americans have killed those journalists had they known they were innocent? I would bet against it.
My point being it's easy to look at the Americans and say they're mindless cannibals with an appetite for war. It's not that cut and dry though.