It's an attachment defense response: if your culture is a favored child, and some other culture is mean to it, you must defend your culture however you can. But

It's an attachment defense response: if your culture is a favored child, and some other culture is mean to it, you must defend your culture however you can. But - crucially - the other culture doesn't have to be mean or actually do anything. Instead it can be a scapegoat for a failing of the child: "We are good and pure here, therefore they are to blame for our troubles." This manifests in incoherent narratives where the enemy is monstrous yet pathetic, strong yet weak, devious yet dumb. Thus, as you see problems pile up with your favored son, you become increasingly infuriated at the outsiders who are to blame, and seek justice against these obvious evils. Swap culture for race, creed, wealth, sexuality and so on and you get all the -isms and -phobias in the world. People who are at ease with the status quo can disengage with their phobias, even if they still lurk in the background. We all have a few, and our emotions try very hard not to let us see our bias up close. As well, the parent-child roles are flexible but recurring, and scale up and down in strange ways: if we beg our government to do more for us, we are the children. If you observe a celebrity being childish on Twitter, the defenders of that celebrity are acting as parents. For a deeper dive philosophical investigation, see Heather Marsh: The Creation of Me, Them and Us.