So just because SOME sermons SUGGEST something you expect it to be instantly made law of the land? From this article...
In 1859 they released from their callings stake president Isaac Haight and other prominent Church leaders in Cedar City who had a role in the massacre. In 1870 they excommunicated Isaac Haight and John D. Lee from the Church. In 1874 a territorial grand jury indicted nine men for their role in the massacre. Most of them were eventually arrested, though only Lee was tried, convicted, and executed for the crime. Another indicted man turned state’s evidence, and others spent many years running from the law. Other militiamen who carried out the massacre labored the rest of their lives under a horrible sense of guilt and recurring nightmares of what they had done and seen. Families of the men who masterminded the crime suffered as neighbors ostracized them...
Looks to me like they tried to follow due process.
"Where was Young seeking to find the perpetrators filling the pews of the LDS church?"
That would be the job of law enforcement officials, not the Church. The fact that Governor Cumming (at the behest of U.S. President James Buchanan) declared amnesty for all hostile acts by any persons in the course of the Utah War hindered efforts to fully investigate and prosecute the crime. Many legal authorities considered MM covered by this amnesty.
"Why was there no open LDS hierarchical investigation and subsequent ex-communication of Southern Utah Mormons?"
Do you think they should have just X'ed them all for being near what happened? The church doesn't excommunicate someone for murder unless there is a confession or conviction in a court of law. It is not the job of the Church to dig into the lives of members and try to find some cause against them. It is the job of the member to confess and seek forgiveness, and to answer honestly when seeking a temple recommend. Yes, that means sometimes people who should be excommunicated might remain as members, but they will just have that much more to answer for to God.
"OK, how then does this author explain that LDS theology had nothing to do with the failure of key Mormons throughout Utah to "out" the murderers, bring them to justice, and properly distance themselves from these murderers?"
It had more to do with history than anything else. Given how often members and church leaders have been subjected to false accusations before (including unfair trials), and how the accusations in this case were of actions so contrary to the character of a good Mormon, it is easy to see how other members first mistakenly believed the charges were just more government persecution.
"The fact is this: The LDS church, no matter what was communicated between Young and his militia leaders prior to the massacre became obvious co-conspirators post-facto and helped to cover up what occurred."
The evidence doesn't support that BY or the Church itself conspired to cover anything up. There were denials by perps, and attempts by some local Mormons not involved in the massacre to shield the accused persons from capture or prosecution because they didn't believe they were guilty and/or that they would not get a fair trial.
#1: What would you think of a, say, Roman Catholic diocese, that took two years to release a few priests from their callings, and another 11 years to ex-communicate them, oh, let's say for "minor dabblings" in mass murder? Exhibit #1: Isaac Haight, the hate Mormon.
The church doesn't excommunicate someone for murder unless there is a confession or conviction in a court of law. It is not the job of the Church to dig into the lives of members and try to find some cause against them.
#2: You said it was the job of law enforcement officials, not the church, to find the perpetrators. Well, again, what if a local diocese knew that a local RC church included dozens of mass murderers? (You mean, no action, no investigation would even be launched? That would be the job of only "law enforcement officials"? And if that's the case, how is it that Haight & Lee got ex-communicated 13 years later--if the role of investigation belonged to law enforcement alone?)
#3: The fact that Governor Cumming (at the behest of U.S. President James Buchanan) declared amnesty for all hostile acts by any persons in the course of the Utah War hindered efforts to fully investigate and prosecute the crime. Many legal authorities considered MM covered by this amnesty.
Any real case of even suggested "amnesty" needs to have real people involved. You can't have phantom victims, and you can't have phantom combatants or perpetrators (combatants if a war covers them; perpetrators if not). The fact that we had mass Utah cover-up of the victims; and the fact that we had no combatants or perpetrators step forward to personally claim the umbrella of war, suggested a phantom apologetic on your part.