You needn't kill a would-be killer. Wounding them will still protect your loved ones while not sending the aggressor to an early grave.
What happens when you need to confront someone on their wrongdoing. They will only hurt themselves and others if they continue in that wrongdoing.
Jesus did not merely tell the woman that He did not condemn her. He also told her to never do it again. God wants to meet us where we are, but not so we can stay there.
There is a difference between judging the sinner and hating the sin.
Not everyone dies at the hand of another. There is such a thing as accidents and dying of old age or diseases.