Echo chamber is one term, another would be tribe. An insecure group member feels threatened by an outsider and lashes out. Another group member sees an outside

Echo chamber is one term, another would be tribe. An insecure group member feels threatened by an outsider and lashes out. Another group member sees an outsider triggering a group member and he immediately jumps into help. Together, they attack the outsider and drive him off. I think if the maintainer was less insecure and more able to take critique, the exchange wouldn't have aroused the "fight or flight" instincts of the group.