I've been watching groups cause divisiveness. Hey you're part of that group, fuck you. You're not in my group, fuck you. I'm thinking we should take people more on their individual qualities. Just because you belong to a different group does not mean we can't find common ground in another group. People are vast, complex and diverse.
This group think phenomena has many names, pack mentality, identity politics, stereotyping, social identity theory, etc...
I bet I belong to the same group as you, we just don't know it yet. Don't be a follower and let your group think for you! Be a leader and see people as the individuals they are.