It's also worth pointing to Tuckman's "forming, storming, norming and performing" stages of group development. The example you describe is an institutional leve

It's also worth pointing to Tuckman's "forming, storming, norming and performing" stages of group development. The example you describe is an institutional level of norming. During the performing stage, which many teams never actually reach, teams can exhibit arse like to outsiders. They have become a unit that fully understands each other, knows how to raise objections efficiently (often read as rude by outsiders), and doesn't want anything to break up the amazing experience that is being part of that team. Adding a new team member into the mix will upset the balance and push the team back to previous stages.