What about all the massacres of Indians happening around the same time, by settlers and military who WERE Mormon?
The Bear River Masssacre, Utah Territory, (Idaho) 1863
The Circleville Massacre, Utah Territory, (Utah) 1866
Bear River was done by the U.S. Military sent there to protect the overland route. Col. Conner was promoted to General after he slaughtered 250 indians, including women and children. Connor was not Mormon, neither were the participants.
I can’t speak about the Circleville massacre, don’t know anything about it.
And of course, Christian leaders were occasionally culpable in the slaughter of Native Americans. For example, I believe the massacre @ Sand Creek (1864) was led by a Methodist minister. But that was an Army attack...a bit distinct from a group of religious people banding together under a single sect umbrella -- and then attacking & slaughtering 120+ men, women & children.