Dojo Kun - literal translation means "training hall rules". There are five main rules that serve as guiding principles for all who train in the dojo. Although they are usually listed in a set order, no one rule is more important than any other. To emphasise this all five are prefixed with hitotsu and end with koto, which together means "one point".
Hitotsu! Kekki no yu o imashimuru koto
I urge you to research the meaning of the dojo kun and to draw your own conclusions as to the true meaning of each rule (start here at Wikipedia). Then, once you've done that, set upon Gichin Funakoshi's 20 Precepts (Niju Kun) and see what you make of them.
Here's my take on Refrain from Violent Behaviour. Of all the dojo kun, this has to be the most paradoxical and one of the hardest to fathom. How can you possibly refrain from violent behaviour when you are learning a martial art? It's all about timing and context. Practicing modes of violent combat in the dojo is the right time and in the right context for such behaviour. Also, the word refrain means to hold oneself back, to be in control of your emotions and your actions. This is a precept (from the Latin: præcipere, to teach) is a commandment, instruction, or order intended as an authoritative rule of action. Drop the commandment and focus on the last bit of that definition; intended as an authoritative rule of action.
This part of the dojo kun is backed up by the term karate ni sente nashi. Here's what the late Taiji Kase Sensei had to say about this:
“Remember what Gichin Funakoshi said ... Karate ni sente nashi there is no first attack in karate. Understand this concept, mentally as well as technically. You must do everything possible so that the opponent understands it is better for him not to attack. This is the true meaning of the saying Karate ni sente nashi that the opponent does not begin attacking and so there is no fight.”
The important points to take note of are, 'You must do everything possible so that the opponent understands it is better for him not to attack ... mentally as well as technically.' 'Everything possible' may mean putting your ego to one side for a moment and backing down from a fight. Demonstrating a kata, or your best roundhouse kick for your assailant is not going to help him understand it is better for him not to attack. So, you need to understand clearly the meaning of no first attack. Strong on in the inside and compassionate on the outside.
A master who is capable of taking an attacker apart, but refrains from doing so when the opportunity to prove the point presents itself is a true master. He does not feel the need to prove to another poor unfortunate soul the sum product of his years of training.