How could Levi have been worthy to hold the priesthood when he was responsible for the murder of Shechem?

Dear Gramps,
I am having a hard time understanding how Levi (one of the 12 sons of Jacob) was worthy to receive the priesthood portion of the inheritance. I have just finished reading Genesis 34 where it appears that Levi and Simeon have committed murder to avenge the abduction of their sister,
Dinah.
Janie, from Ohio
Dear Janie,
It is difficult for us to make specific judgments across some 3,500 years of time, and to assess the particulars of the cultures of those days. Nevertheless, the principles are assumed to be invariant, but they must be judged in light of the hearts, the laws and the societies of the times. First, let’s look at some actions that would invoke our harsh judgment if they were to occur in our time or if we were to impose our mores on other peoples. What about all the sons of Jacob who condemned Joseph to die by putting him in a pit from which there was no escape, so that he would starve to death? And how about the Lord imposing the death penalty for such a sin as cursing one’s parents, (see Leviticus 20:9)?
But the fact is that the promises that effected Levi and all his brothers were not made to them but to Abraham. And those unbelievably marvelous promises made to Abraham were confirmed on his son, Isaac, and on his grandson, Jacob, the father of the those for whom the twelve tribes were named. So my opinion is that those marvelous promises that affected the salvation of the world by providing priesthood authority and leadership for the kingdom of God on the earth, and for exaltation in the eternities, which includes the right to rule and reign in the house of Israel forever, were passed on to all the progeny of Abraham, Isaac and Jacob. If any of them sinned against the Lord they were undoubtedly duly punished, according to the law, but the wickedness of one man could not negate the great plan of God for the salvation of the whole human family.
Gramps