People kill for all sorts of reasons. But they also commit adultery for all sorts of reasons, lie for all sorts of reasons, steal for all sorts of reasons, etc. etc. All have sinned and fall short of the glory of God. It boils down to the fact that people are sinful and fallen beings in need of a Savior. Even you are in that category friend. Isn't it true you have broken the 10 commandments in your lifetime? Have you ever lied - even once? The bible says if you offend in one point of the law, you are guilty of all. Without a Savior, you or I will surely be judged for our actions and will spend eternity separated from God in hell.
I'm sure you are correct about the teachings of Jesus, but that hasn't prevented Christianity, as embodied in the Church, from committing murder, and in fact doing so for centuries at a time.