That first sentence so reminded me of the famous animal farm which I do believe the same line was said, and funnily the same problem happened there too they all turned on it's leader in the end.
Taking another life in justification is a hard question to answer, I think often of such subject and law its self, what we ourselves percieve to be right and wrong which I wonder if most of it is based on feeling alone when the outcome has been reached.
Infact to be honest until the day we reach contact with other civilisations in space which I believe there are we will never truly grow as a race, because we don't comprehend how small and insignificant we actually are, in the grand scheme of things.