Two words..
Kent State!
When the American Indian Movement activists were besieged at Wounded Knee in 1973 the Govt deployed portions of the 101st against them. They were put in blue cover all's and called "deputies", but they were Army.
It has also been proven that Army and NG assets were used in the massacre of the Branch Davidians in Waco.
Look to history, The Nazi and Japanese troops who committed atrocities during WWII ( and I am NOT talking about elite forces like the SS ) were not some kind of monsters. they were ordinary Germans put into extraordinary situations.
Bormann, Eichmann, Himmler, the others who gave the orders, despite the propaganda, were not bad people, they were in fact frighteningly ordinary people who were actually pretty good at their jobs, faced with situations that were out of the ordinary.
The extermination of the Jews did not begin as some diabolical plot by ogre's who ate babies for breakfast.
It began with messages to Camp's, "You are getting 20,000 prisoners on Thursday." "But I don't have room."
"That is not relevant, the trains are already on the way."
(
There was a book about this, "The Banality of Evil", I don't remember the author. )
The greatest brutalities of the Bataan Death march did not occur because the Japanese were little Yellow demons, they happened because the Japanese had never planned on taking such large numbers of prisoners, they therefore had no facilities or supplies to deal with them.
There is absolutely no reason to expect Americans to perform any differently, and plenty of reasons such as My Lia, or New Orleans to assume they will act exactly the same way.
When it does not involve mass murder it is considered a good thing for people to "get it done" despite difficulties, or when proper tools are not available.
It's the dark side of a "Can Do" attitude.