I have never heard of such a thing in my history books or any where else. yes some Mormons like Christians or atheists have committed massacres in the name of their beliefs. It is sad that some will take a mentally ill person and use that to label a whole religion of belief system.
Cults do exist and often hide behind the facade of a well known belief system to con others in.
I think that the Church can not be held responsible for the action of one its member committing a felony.
Here is why:
If your boss who is the authority of your work place decides to change the practices of the company with out the companies knowledge or permission is that company now liable if he shoots you due to the changes he made in the policies he was left to enforce?
I work with electricity we have strict policies and procedures. By law if I go out side of them the company is no longer responsible for my actions. Why should the church be different?
I think they are responsible if the whole act was done as a religious killing and with the leadership of a local leader. If you are a father and one of your sons goes out and kills someone because you told him that he should then you are also responsible as his father. Leaders are responsible for their flocks and what they do.
Yes if I did I would agree but then does that mean my father is also guilty though he did not teach me this way?
No he is not thus if a Mormon leader kills you must prove the church taught him this and told him to do this.
You must be sure that he did not misinterpret some doctrine. Cult leaders often take a perfectly fine piece of doctrine then twist it to fit their agenda.
Ok I will try to make this more clear.
If I teach a man all I know based on sound doctrine and values. In turn he takes a handful of those points and ignore the rest and then you teach just the tings he liked as they fit his views.
He in turn teaches only that which he accepted as being true and uses just a small portion of the teaching to do some thing evil. Can I know be held accountable for his actions? No as he did not use my teaching he developed his own. That is why many end up referred to as a cult leader.
There is something called, "The lone wolf", that is where a church will preach that gays, or any other sin, are sinning against God and will read passages in the Scriptures that says that lying is a sin big enough to kill them, and tell the Sodom and Gomorra story where God burned the two cities for mainly the population is gay. While never actually saying it, the church is saying that killing someone that is gay is ok, but publicly will say that the church had never taught to kill gays, and although that is true, it is like telling someone that all sin is bad, and punishable by death, but then say that they aren't responsible when someone in their church kills someone that is gay.
In the Mormon church there is no honor killings, however I can almost understand why someone would try to keep the family's honor by killing their son or daughter that does drugs, get pregnant before marriage, or anything else that dishonors the family's name.
The Mountain Meadows massacre was a horrible event in Church history. The people involved acted alone, hating being prosecuted against, and wanted to act back, and get back what was rightfully was theirs. As dbackers stated, the local leaders that were involved were tried and convicted for their crimes.