There is a Book of Mormon verse we never talk about.
Alma 43: 46 And they were doing that which they felt was the duty which they owed to their God; for the Lord had said unto them, and also unto their fathers, that: Inasmuch as ye are not guilty of the first offense, neither the second, ye shall not suffer yourselves to be slain by the hands of your enemies.
Now THAT is an interesting doctrine. It says that if you are guilty of neither murder nor adultery then you are not to suffer yourselves to be slain by the hands of your enemies. And of course, what is interesting is the exclusion there. It specifically does not cover those guilty of adultery or murder.
I expect Brigham Young discussed the meaning of it one way or another. It appears to mean that if you are guilty of murder or adultery then you have lost the right to take someone else's life in defense of your own.
So it does seem that one can lose the right to take a life to protect one's own life by choosing either murder or adultery. One may find that one's life may not be forfeit for murder, and it certainly isn't forfeit for adultery, but either way one's right to take another life to defend one's own is apparently lost. It doesn't mean no one ever did it. Many have. But it states something about what rights we have, how our actions can change them, and how the grand tally will be taken at the final judgement.