Powell was a peripheral party to the My Lai concealment, although more by omission than intent. Asked to make a preliminary investigation into rumours that civilians had been murdered, he wrote a report for his army superiors conceding there had been 'isolated instances' of abuse but added that 'relations between Americal soldiers and the Vietnamese people are excellent'.
This time around, older and presumably wiser, he appeared entirely genuine in his revulsion for the horrors of the Abu Ghraib prison and its US military police guards. His chief of staff hinted strongly that Powell will not stick around if George Bush is re-elected in November.
It's worth making the point Abu Ghraib is not an isolated instance of the isolated instance line.