Thank you for the quotation from Grant. I had never seen that before. (Do you have a citation that I could store?)
As to the other references, the outrage of General Holt, the Army jurist, follows the trend of revulsion at the acts, calling the massacre cowardly and shameful, (or, in my earlier words, “Horrifying, repulsive, but not necessarily murder”) but he does not go so far as to call them murder–and the Army allowed Chivington to resign his commission without ever bringing him to a court martial, nor did they court martial any of his subordinates or any of the troopers who brought home and displayed their grisly souvenirs.
Similarly, the reference to “massacre” in the Congressional report does not seem to include the word murder. While the word massacre has had associations of murder at various times, it is generally used as a description of wholesale slaughter, regardless of the motives of the participants, and has been used to describe actions as disparate as the Sand Creek Massacre and the destruction Fetterman’s command in open battle.
Many people were horrified by the actions of the Colorado Volunteers, particularly with the reports of women and children having been sexually mutilated and the severed body parts displayed as trophies. The massacre was generally condemned throughout the country. Can you point to a single call for a trial for murder?
If you can come up with a rather longer list than General Grant, Captain Soule, and J.W. Wright, I will acknowledge that more people saw Sand Creek as murder than I had been aware. However, as to generalizing about the attitudes of whites in the U.S., the reactions to Sand Creek still do not translate to a general condemnation of the 1852 Bridge Gulch Massacre, the 1863 attack on the Shoshone, the 1868 attacks along the Washita, or the “Battle” of Wounded Knee. Even the Camp Grant Massacre probably went to trial as much or more because the majority of the attackers were, themselves, indians (and all those charged were found not guilty).
Such massacres were often seen as wrong, because “we civilized people should not do that sort of thing,” but they were not generally looked upon as the unlawful taking of life.