Study up on feuds and vendetta and see how beautifully it worked out for the families involved and for their societies in general.
It might not have worked well for the few families - but it certainly worked for the societies. While being culled out by each other, the families with wrong culture/genetics served as a good example for others.
As for politeness, we - humans - have instinctual urge to meet any real or imaginary slur or offence with confrontation, even if it's a bluff. Getting confrontational might get you hurt but being perceived as meek was much worse procreating-wise in the days of hunter-gatherers. Evolution hardwired those emotions into us.
Now, when I have a gun with me, when I know that I am equal to anyone, regardless of size or number - I
feel safe and confident. I
feel much less emotional when someone slights or offends me. I
feel less urge to engage in aggerssive confrontation. I also
feel no fear and get no surge of adrenaline - which keeps me rational and less swayed by emotions.
While someone acts like an a-hole, I can quietly consider the options, chances, reprecussions, venues of retreat and lines of fire.
So I am polite, yielding and forgiving. My blood pressure is stable, my visage is serene. There is no thought involved, let alone consideration of future legal issues.
miko