Basic human society. Hunters and gatherers did it too.

People formed tribes to build a circle of trusted people, those outside the tribe were not trusted by default. It was a basic survivval technique. Tribesmen who broke the trust were kicked out. People who wanted to join the tribe had to prove their trustworthiness.

Inclusively people are a global tribe. You are not in the tribe because you have proven yourself not trustworthy. You cannot be trusted to treat all tribe members with respect. If you want to be back in the tribe, you will have to prove yourself.