It took the Church until 1832 to remove Galileo 's work from its list of books which Catholics were forbidden to read at the risk of dire punishment of their immortal souls.
It isn't the desire to abide by the law that makes everyone behave as society requires, but the fear of punishment. Each one of us carries a gallows inside us.
But secondly you say 'society must exact vengeance, and society must punish'. Wrong on both counts. Vengeance comes from the individual and punishment from God.
Ignorance itself is without a doubt a sin for those who do not wish to understand; for those who, however, cannot understand, it is the punishment of sin.
Capital punishment kills immediately, whereas lifetime imprisonment does so slowly. Which executioner is more humane? The one who kills you in a few minutes, or the one who wrests your life from you in the course of many years?