Because humans are born with their foot in their mouth and their head up their ***. A selective few grow out of that.
Because people confuse "different" with "better".
Because people are ethnocentric and it is very natural. The same way that you value your own family above the next door neighbor even though you really like them is the same way that races and ethnicities first favor themselves. I lived in France for the first decade of my life and while the French were very racist toward Algerians, they didn't care much about blacks because there were few. Then, I went to Georgia and didn't think anything of blacks because no one had taught me. One day I was in Sears with my grandmother and I went to the water fountain and as I bent my head she grabbed my hair and almost yanked my head off. She hissed at me and pointed to the sign--Coloreds Only. So, ethnocentricity is rather ingrained, but racism is taught. In 1965, if you were black anywhere in this country and wanted to take a drive someplace--you had to pack your own food and water because you couldn't go in any place that wouldn't have you, and that includes the north and you certainly weren't gonna find a motel. People forget that that kind of racism was common place in this country until LBJ's Civil Rights Act. But, it started with the delegates from Africa coming to DC for Presidential Dinners at the White House and JFK realized that they could not eat anywhere in DC. Lincoln freed the slaves but they didn't get the right to be human till '65. In the south, in the 1870's white men would walk down the street and shoot every black men they saw. US Grant wanted to do something, but he knew that he couldn't. He said that it would take a hundred years for the stigma of slavery to wear off. And it did, but racism still abounds.
Immaturity. All outdated values accepted in the past will be radically replaced with new values conceived by the mature human race.
Because some people are ********.
It's human nature to be judgemental esspecially when it is passed down through generations. Children are'nt born hateing it's what we teach them. To stop the hate we have to start with the new generations.
It's basic human nature, although much more prominent where people are undereducated.
because of the aliens