In-group bias

What it is

Favouring members of our own group and viewing outsiders less generously.

Example Excusing a teammate's foul and condemning the same foul from the opposition.

Groupthink bias
Strong in-group loyalty makes dissent feel like betrayal.
Guilt by association fallacy
Linking someone to a disliked group works because we treat group membership as telling us everything, which is the engine of in-group bias.
Stereotyping bias
Stereotypes are applied most harshly to outsiders.
Disliking/hating tendency bias
Dislike of the out-group is the flip side of favouring the in-group.
Social comparison bias bias
Comparisons are most keenly felt with people in our own group.
Unity bias
Shared identity makes "us" and "them", which in-group bias exploits.
Not-invented-here syndrome bias
Rejecting external ideas is in-group bias applied to ideas.