What if violence/murder was not considered immoral?

Often I've pondered that question. How would our society as well as our government be formed differently if murder and other acts of violence were not considered so incredibly immoral? How would the average person's mind differ in its priorities if it was a regular thing to learn how to defend yourself? How much more of an impact would the philosophies taught by martial arts have on our way of thinking as a whole? Well, let's take a step back with this question: Why does our government hold murder as the highest offense against the law?
Well, the answer is pretty basic--the taking of another person's life is the most effective way to involuntarily restrict their freedom--which is why I'd like to analyze it. It's a primitive answer to a stupid question. It's a lot more fun to get something meaningful out of it.
What is so intriguing about such a simple answer is that it's based on our most basic cultural thinking. It is not uncertain to the average American that killing someone will do little more than end their life permanently. We are so bound by this cause & effect belief that we never consider other cultural points of view to have any truth in them. And because of such a belief, we also believe therefore that murder is the most terrible crime; so terrible in fact that we sometimes find the most justice in taking the life of the murderer as well.
How does this compare to the Japanese way of thinking? Well first of all, in Japan, Shinto-do caused its disciples (all people of Japan at one point) to look at violence and murder very differently. The Japanese believe as part of common sense that humans are not physical beings, but spiritual inhabitants. One's own spirit is not fully bound to the body they are given. It could be drawn out, dispersed, concentrated, or even bound to another spirit/object/animal/person. From this basic belief branches all the things about Okami and Oni, spirits unbound by physical substance, but often taking the form of animals or objects. For instance: Amaterasu, the Okami of Life, is often portrayed as a dog. On the other hand, many Oni are portrayed as dolls or flying swords.
Even if many Japanese are/claim to be Buddhist or even Christian these days, this way of thinking brought on by Shinto-do is still present insomuch that even today their everyday speech resembles it. In Japanese one does not say "My hair is brown", they say "The hair is brown". Or, more accurately, "Hair-[on top of head] [subject marker] tea-colored [positive statement marker]". Your body and its faculties are not your possessions. That's not to say there's no such thing as personal property. Japanese does in fact have possessive speech: a donut can and often will belong to someone (so be warned). People still say "She is my mother", "I am your* servant", "Get your* hands off my donut!", and "This is my table and if you don't move now I'll cut you to pieces!". (*There are two different words for "you": Anata and Kimi, which mean "you" and "this/these/those not of 1st person addressing nearest 3rd person", respectively.)
So you can hopefully now see why, at least in ancient Japan, the ideas of murder and violence weren't considered so morally wrong. To remove someone from their body usually didn't mean much more than that. There were of course laws against killing someone against their will, that is, unless the Emperor willed it so. Then in the later centuries there was a time when unsanctioned duels between Samurai were strongly discouraged. Eventually it became a law for all Samurai that they could not challenge or accept challenges. This wasn't because killing was considered wrong, mind you. It was simply because as the Samurai went, they were very hard to replace, and they were only useful to their lords when they were alive and in good health.
It was a large part of Bushido that a Samurai should always be prepared to die. That is ultimately what carrying a sword meant: death, either on your account or the account of your enemies. So really there was no way to unlawfully kill a Samurai. The only problem one may have faced is being able to kill them. Understand though that, as highly trained as any Samurai was, they were careful to not become so prideful that they may have thought themselves invincible. No, an honorable Samurai was one who, upon brandishing his sword, knew that his life was at just as much mercy as his enemy's. Not that he doubted his own abilities, but he was at least wise enough to know that no amount of skill could ever temper someone's skin against the cutting edge, should their own skill fail them.
In modern society we fall very short of that way of thinking, because killing to us is so wrong that we think nothing of it. Civilized people don't kill each other anymore (I myself beg to differ, but that will be a different blog, possibly). When it comes to violence and combat, people are so shallow these days that they seriously believe a gun is more effective than a sword in every conceivable situation, and that pointing one at someone and pulling the trigger will somehow magically kill them. Does this not also effect the way we think in other situations? Take guns to be the easier path. We often take the easier path, thinking it will always be sufficient and just as if not more efficient than the harder path. How would being trained with firearms, blades, other weapons, and martial arts effect our way of thinking?
Perhaps then there would be a higher standard for "common sense".

Please do not take this as me supporting or glorifying violence. To me it deserves less of a place in our society than sports and entertainment. That doesn't mean that what can be learned from insights of combat cannot be applied to everyday life, and that is why I think we all should study combat seriously and sensitively, no matter how much our society condemns it.