Passions ran high in Mormon culture back then. Brigham Young had two guys, Hickman and Rockwell, who would disappear anyone who made Brigham unhappy.
Then Brigham drew a map of the Mountain West and declared a great big chunk of it a separate and sovereign country. The Feds sent the army out to abort that venture.
So along comes a wagon train of gentiles headed west and the locals saw it as an opportunity to get some revenge.
Look up The Hawn’s Mill Massacre and other ‘Christian’ acts toward Mormons before you speek about what early Saints went through.
Mountain Meadows was wrong, but your rendition of reasons is worse..
… Captain Comstock, who previously had assured the Mormons at the mill of their safety, had returned the next day attacking them, saying he had received an order from Governor Boggs via Coronal Ashley
(Snip)
Shortly before the massacre, anti-Mormon raiders confiscated gun and weapons from Mormon settlers and immigrants.[9] Some of those living in the surrounding area gathered to Hawn’s Mill for safety.
(Snip)
On October 30 at approximately 4 p.m., the militia rode into the community. David Evans, a leader in the community, ran towards the militia, waving his hat and calling for peace. Alerted to the militia’s approach, most of the Latter-day Saint women and children fled into the woods to the south, while most of the men headed to the blacksmith shop. Unfortunately, the building was a particularly vulnerable structure as the widely spaced logs made it easy for the attackers to fire inside. The shop became a deathtrap, since the militia gave no quarter, discharging about 100 rifles into the building.[10] Grand River Township Justice of the Peace Thomas McBride, wounded while escaping the blacksmith shop, surrendered his gun to Jacob S Rogers Jr. who shot him, then hacked his body with a corn knife (scythe blade). According to their own account they fired seven rounds making upwards of 1,600 shots during the attack of Hawn’s Mill.[22] The attack lasted 30 to 60 minutes. The sun set at 5:16 p.m.[23]
(Snip)
Members of the militia entered the shop and found 10-year-old Sardius Smith, 7-year-old Alma Smith (sons of Amanda Barnes Smith), and 9-year-old Charles Merrick hiding under the blacksmith’s bellows. Alma and Charles were shot (Charles later died), and a militia man known as “Glaze, of Carroll county”, killed Sardius when he “put his musket against Sardius’s skull and blew off the top of his head.”[24] Later, a William Reynolds would justify the killing by saying, “Nits will make lice, and if he had lived he would have become a Mormon.
https://en.m.wikipedia.org/wiki/Haun%27s_Mill_massacre