A few weeks ago there was a well-reported incident in which a Marine commander who opposed both the attack and the later withdrawal from Fallujah described it with the words “revenge” operation (he didn’t call it a massacre). I didn’t clip it, but it shouldn’t be hard to find. It was well-reported and elicited editorial comment as well.
But we hardly needed that. The Marines invaded Fallujah in immediate reaction to the killing of four US military contractors. They didn’t try to apprehend those involved, but carried out a large scale attack which was in fact a massacre. That’s “revenge”, even without the explicit acknowledgment. Just as the killing of the contractors was revenge for the US-Israeli assassination of the quadriplegic cleric Sheikh Yassin (and half a dozen bystanders) outside a Mosque in Gaza a few days earlier.
Revenge for 9-11 and operations against US troops in Iraq is a different matter. There have been plenty of reports in the press about attitudes of US soldiers, taking revenge for 9-11. There was a full-page NYT presentation of soldiers with pictures back in the early stages of the invasion, with their comments about why they were eager to fight in Iraq. Much of it was pay-back for 9-11. The basic principle is that all Arabs-Muslims are alike, so even if Iraqis had nothing to do with it, they’re responsible. And there have been repeated examples since.