What allows people to get along and not kill each other?

Emphasizing what they have in common rather than emphasizing what is different about them.

So, emphasizing what we all have in common is the likely way for people to get along.

However, if one of these people suddenly draws a knife, sword or gun and uses it all bets are off of course.

IN fact, travel in Great Britain was based upon this exact thing. Most people are right handed so if you were walking down a road where people pass you on the left this was done so you could see this person more easily draw their sword from their left hip.

So, the people walking and the wagons going to your left past you all came from wanting to see if someone was drawing their sword on you so you could draw your own sword in time to defend yourself.

Also, in Great Britain if you ever wondered how roundabouts came into being it was caused by horses pulling cannons for war.

Once you get cannons stopped moving it is really hard for the horses to overcome inertia to get them moving once again. Often they have to rear up to get enough forward force to start a stationary wagon moving once again and this can damage horses putting this much force on their rear legs when they are forced like that to rear up to get enough forward force to overcome inertia because of the weight of the cannons.

So, roundabouts were started as a way to avoid harming horses by stopping needlessly. You don't pull cannons very fast usually so as long as they were moving any speed at all they usually could keep moving them at some speed until they reached their destination.