Turn the other cheek was taught by Christ - to whom? Christ was training Disciples, to become Missionaries. When on the mission fields, try not to offend, but if you do, and causes a slap to one side, then offer up the other side also. This requires focus, and meekness.
The Word teaches us to "love our neighbor". What if a neighbor, or anyone else slapped our face? They should immediately be taught the error of their behavior. We are to live in peace - it at all possible. But sometimes, it is not possible. We have the authority from our Creator to defend ourselves and family.
The Word [King James Bible] defines and explains murder; unauthorized killing, laying in wait, or with hatred in heart. An unprovoked assault resulting in the attackers death result in the blood being on the attackers hands. There are violent people on the earth; some have declared war against others, especially against Christians. They come with hatred in their minds, and see Christians as soft for their refusal to stand.
Abraham fathered Ish'ma-el, but had to run him off when he refuse to get along with I'saac. Distance sometimes is successful; but the are frequented by Abraham, later turned into the center of Babel. The descendant of Ish'ma-el continue to hate and refuse to get along with others to this day. Because of "PC", which comes from the Satan, people are almost paralyzed. Christian are being stung by the scorpions of Revelations, and are shocked into paralysis.
Mature Christians should be prepared. Jehovah's rules are contained through-out the Operators Manuel that He gave us. The flip side is a 'copy right' book, containing the "Traditions of men". The trouble is here, right now. We are Not to be caught flat-foot or in neutral. Look to the ant; tamper with, or attack a fire ant mound, and observe the response.