I think most people are upset with the Iraqi prison photos because they reflect so poorly on the United States. For the most part, it's human nature to disregard news that makes us look bad.
For instance, we never hear anything about the tens of thousands of civilians dead in Iraq. Word is that a soccer field was bulldozed to bury all the bodies of Iraqi civilians killed by the United States.
So the latest mass graves in Iraq are ours. What people focus on is the intention. We didn't mean to kill all those people. And for most people, that's a good enough explanation.