If we belong to or identify with a group, than we will regard that group to be the ‘in group’, anyone outside this group will be the ‘out group’ and therefore they become the ‘not us’ or ‘them’. This orientation will trigger our tribal behavior and we will become extraordinarily contemptuous of, cruel towards, and paranoid about ‘not us.’ Because we know that other groups can be hateful and as paranoid as we can be, we fear them; and so continue the cycle of hate and paranoia. In certain context, we may even attribute cruelty as a virtue. Around the time of 911 crisis for example we may remember certain cruel acts on both sides were not uncommonly reported in the media, depending on which group you were in, it was either interpreted as an act of cowardice or heroism; same cruel act but interpreted as a virtue by one group and cruelty by another. This kind of behavior has been a source of great suffering for thousands of years.
Why does this kind of behavior continue? One answer is that we derive our self-identity from the group to which we belong and adopt its values. The group then orients us to compare ourselves to others; and as we get comfortable with the idea of belonging and being accepted by our group, we seek to have our contribution valued, wanting validation that our existence matters to the group. A sense of belonging is important to feeling of well-being and feeling safe. It is the sense of belonging that keeps us in the mode of the ‘in group’ and noticing the differences in the ‘out group’. This is a tribal behavior and it is this that keeps us from being compassionate to other groups and will keeps the suffering to continue unless we change our tribal thinking.
The Compassionate Mind by Paul Gilbert