Cliques.

No. This is not some angry, isolated teen's writing. It's not personal. Just educational.
We need to get out of this state of mind of people not belonging to a certain group. Of having a particular kind of people we interact with. It's completely senseless only having with the same people. Do not shun or bring other people down just because you don't hang together. Just because they don't belong.
It's wrong and it's one of the problems of our generation.
Get out of your comfort zone and just say hi.
It's not difficult.