Polite Courtesy
Samurai have no reason to be cruel. They do not need to prove their strength. A samurai is courteous even to his enemies. Without this outward show of respect, we are nothing more than animals.
This also is a reminder about the warrior mindset during a life protection situation. A warrior should not be angry when fighting. The warrior should be serious, but calm. If you resort to anger, you have already been defeated.
*Note* When the word "samurai" is used, it refers to any warrior from Japan and/or Okinawa.