God gives us the laws of universal morality. However, with free will, we can choose to follow them or not. This is why there are differing places in the resurrection where people are assigned. It would be hell for the moral to be consigned forever to live with the immoral. And the immoral would not have the character to abide by the moral law.
So you think the morality of the OT is the same as the morality of the NT? I don't recall turning the other cheek in the OT.
Jesus said you have been told an "eye for an eye",,etc...,referencing the personal injury law, "you must require a life for a life— eye for eye, tooth for tooth, hand for hand, foot for foot, burn for burn, wound for wound, and stripe for stripe." Its basically teaching equal and measured justice under the law so that someone who punched you in the eye didn't get the death penalty.
A slap on the cheek isn't even on the list. A slap on the cheek wasn't even considered an injury. At the time it was an insult, Thats how slaves were treated and people would seek retaliation in court for being humiliated not injured, a waste of time. "turn the other cheek" is more like sticks and stones . It was not a teaching that people should not defend themselves against violence.
Pop quiz!
What creature high or low, of all the livestock, of all the wild beasts of the field, of all the beings in heaven, on the earth, or under the earth would teach people to just stand there and take it and then say, "Thank you Sir. May I have another."?