Why do arabs have racism toward one another?

Besides the racism that arabs face from the western culture, there is racism between the arabs themselves. There is racism between jordanians, syrians, saudis, lebanese, and many others. Why? Oh and there is a lot of hate toward egyptians from many arab nationalities too. As an egyptian, I suffered in my high school years living in the middle east. Racism, hate, and humiliation beyond what you could've imagined. Aren't we suppose to be like "together" and all? I need good answers that could help me answer my question not make me think of deleting it.