The basis for all perceived racism is a global phenomenon known as Tribalism. It can be as local as your neighborhood, circle of friends and family. It stretches to regional and ultimately nationally. Typically, it comes down to whether you are affected by something that is said, but also the actions of people far and near. A good example is the joke I posted earlier. You might laugh, or you may be offended. It depends on your view and whether you feel that your circle has been insulted. An Italian guy might find it funny, but change Polish sausage to Italian sausage and see what may happen.
Moreover, it doesn't stop there. If you can't finger someone for their race, you will discriminate for something else, like their appearance or or anything that you can quickly identify. Example: someone cuts you off while you're riding. You speed up to see who's driving. It's a Chinese guy. "Why... you Chinese son of a *****", you may say. The next day, you are again cut off. You look and it's a white guy. You look for something to identify what's different from yourself. "You fat son of a *****", "you bald son of a *****", "you short little son of a *****"...
There's obviously more to it than that. But you get the idea. That's why some people want to run off and join ISIS. They want to be part of that tribe. And ISIS is a perfect and extreme example of tribalism: wanting to kill your brethren that do not agree with your narrow version of the same religion.
Moreover, it doesn't stop there. If you can't finger someone for their race, you will discriminate for something else, like their appearance or or anything that you can quickly identify. Example: someone cuts you off while you're riding. You speed up to see who's driving. It's a Chinese guy. "Why... you Chinese son of a *****", you may say. The next day, you are again cut off. You look and it's a white guy. You look for something to identify what's different from yourself. "You fat son of a *****", "you bald son of a *****", "you short little son of a *****"...
There's obviously more to it than that. But you get the idea. That's why some people want to run off and join ISIS. They want to be part of that tribe. And ISIS is a perfect and extreme example of tribalism: wanting to kill your brethren that do not agree with your narrow version of the same religion.