It seems to be a sad trait in human nature. We seem to have a need to be part of a group, to feel like we belong to certain social clique, be that your religion, or football team, race, gangs, what music you like anything.
Some people turn everything in to us vs them. Look at how they are different from us. It upsets me dearly when you consider all the knowledge we have gained from sharing our ideas and culture that we still find the need to divide ourselves based on lines on a map or whether you have a penis or vagina.
Just silly.