Here is FAIR's fact checker of the Mountain Meadows portrayal.
Clarification:
While it is true that Mormon militia members, along with some Native American recruits, attacked the emigrant wagon train, they did not initially kill all the emigrants. The massacre occurred in phases, and some individuals, including children under the age of seven, were spared. Furthermore, Brigham Young was unaware of the attack until after it occurred.
Explanation:
The Mountain Meadows Massacre took place in September 1857, involving a wagon train of emigrants from Arkansas. A few members of the local militia from southern Utah, along with a few Native American recruits, may ha{ve} initially attacked the emigrants disguised as Native Americans. After a prolonged standoff, the emigrants surrendered under the promise of safe passage, but most were subsequently killed, except for 17 children under the age of seven who were taken in by local families until they were returned to relatives. Brigham Young’s role in the event has been a subject of historical debate, but contemporary evidence—including the testimony of James Haslam—indicates that Young actively sought to prevent violence. Haslam, who rode 300 miles in three days to deliver a message warning of potential conflict, stated that Brigham Young instructed him to tell local leaders to protect the emigrants and avoid any harm. Haslam’s message, however, arrived too late. Young’s reaction upon hearing of the massacre was reportedly one of sorrow and anger, not complicity.
https://www.fairlatterdaysaints.org/hom ... n-primeval
So they take issue with the portrayal of it happening in one event, rather than a more prolonged and terrifying series of events for the victims. They attempt to downplay Mormon involvement by using terms like "They did not initially kill all the emigrants", "some...were spared", "A few members...a few Native American recruits...", "...may have initially attacked the emigrants disguised as Native Americans".
Here is an official Church recounting of the event, which shows the FAIR attempt to disparage American Primeval to be mealy mouthed at best.
In September 1857, a branch of territorial militia in southern Utah composed entirely of Latter-day Saints, along with some American Indians they recruited, laid siege to a wagon train of emigrants traveling from Arkansas to California. The militiamen carried out a deliberate massacre, killing 120 men, women, and children in a valley known as Mountain Meadows. Only 17 small children—those believed to be too young to be able to tell what had happened there—were spared.
https://web.archive.org/web/20220926174 ... e?lang=eng
The arrival of the wagon train in Utah Territory occurred in the midst of a period of “reformation” within the Church. Concerned about spiritual complacency, Brigham Young and other Church leaders delivered a series of sermons in which they called the Saints to repent and renew their spiritual commitments.1 At times during the reformation, Brigham Young, his counselor Jedediah M. Grant, and other leaders preached with fiery rhetoric, warning against the evils of sin and those who dissented from or opposed the Church.2 Such preaching led to increased strain between the Latter-day Saints and their relative few neighbors in Utah, including federally appointed officials.
That's Brigham Young rallying his troops to action, inciting them to violence.
Over the next few days, events escalated, and Latter-day Saint militiamen planned and carried out a massacre. They lured the emigrants from their circled wagons with a false flag of truce and, aided by Paiute Indians they had recruited, slaughtered them. Between the first attack and the final slaughter, 120 were killed.
As Gadianton points out, American Primeval, if anything, makes the Mountain Meadows Massacre less horrific than the Church admits it really was. Brigham Young inciting his people to arms was directly responsible for the increased state of tension and alert that led those Mormon militiamen to do what they did at Mountain Meadows. FAIR's weasel words and attempted downplaying on the subject denigrate the memory of the victims and they should be ashamed of themselves. At least their Church (belatedly) admits the reality of the event.
Despite FAIR’s cheap attempts to exonerate Young from all responsibility for the Mountain Meadows Massacre…
After the massacre, Young stated in public forums that God had taken vengeance on the Baker–Fancher party.
https://en.m.wikipedia.org/wiki/Brigham ... s_Massacre
That’s Young glorifying the massacre as God’s work.
When Young sent his report on the massacre to the Commissioner of Indian Affairs in 1858, he said that it was the work of Native Americans.
https://en.m.wikipedia.org/wiki/Brigham ... s_Massacre
That’s Young knowingly lying about the event, putting the blame on the Native Americans and hiding Mormon involvement.
FAIR might want to factcheck their factcheck.