[recycled sixtie]

It is natural for any group of like minded individuals to initiate their way of thinking. Take for instance those proposing sharia law. Generally speaking majority rules. There will always be incursions and pressure from other groups. This is normal in peace time. However when the chips are down and a big war is impending such as WW2 then the various groups combine to fight the oppressors. Look at the number of First Nations people who joined the armed forces during WW2.

On a micro level if my neighbors' tree roots grow in to our yard then you get the idea....