Let's back out a bit. You said most of the casualty was caused by Iraqis using their own people as human shield when US invaded.
You are taking my words out of context. The original charge of the Intercept article was that Mr. Mattis is personally responsible for the civilian casualties of numerous battles, including (and the one I'm focusing on) that of Fallujah. The mention of "human shields" is to emphasize that civilian deaths arise from numerous causes, and until a thorough investigation is conducted on the military/non-military factors that resulted in those civilian casualties, we cannot pin those deaths on any single individual, especially when insurgents (in Iraq and elsewhere) have been known to either attack civilians or use them as leverage against US forces.
And I said US had no business to be there to begin with. When you decide to occupy a country in less than three months, you will intentionally ignore a lot of humanitarian fundamentals other wise, it will take much longer.
Humanitarian fundamentals may not have been a top priority of the brass that made the decision to enter Iraq, but you can be certain that they existed within the day-to-day soldiers who carried out such operations. Until it is concluded that Mr. Mattis had either (1) operated via misconduct or (2) neglected military protocols that led to civilian casualties, however "wrong" the Iraq War was has no bearing on his guilt (or innocence).

,indeed I have a sneaking suspicion that not only would the captain and likely some of his senior officers careers have come to a sudden and screeching halt
[to put it mildly],actually I think that probably would have been the least of their worries at that point as I strongly suspect they would be facing a general court-martial on some extremely serious charges that if proved would not only completely and utterly destroy their naval careers but would also very likely result in a significant loss of liberty as well.



