It is not true to say "scripture doesn't contradict itself." Many times Jesus corrected the scriptures by saying "It is written... but I say unto you...." e.g. "an eye for an eye, but I say unto you do good to those who do evil to you." An eye for an eye is a limitation, not an excuse for murder, state-sponsored or otherwise. You can prove anything by scripture, as in the famous example of "Judas went and hung himself" and "Go and do likewise." Serpents have agile tongues and often are skillful manipulators of scripture.