Can't tell if Troll or just very stupid.
Seriously, though, Racism is all about History and our preconceived notions of peoples based off said History, aka Stereotypes, with a little Religious under/overtones thrown in for good measure.
Why are white people racist towards black people and vice versa? Slave Trade. Pure-bred Africans, living in the plains of Africa with none of the "necessities" of life that we take for granted - like, oh say, plumbing, electricity, and the like - were considered "inferior" because of this, and because Christians believed everything God put on this Earth is theirs for the taking, someone decided that because Africans didn't "look" like them, that they "weren't human" and thus could be used as slaves. So, yeah, some white people may still have it hard-wired into their minds from years of inbreeding that African-Americans are still inferior, and most African-Americans fear that there are more people like that than there really are, so it's just easier to adopt the "guilty until proven innocent" doctrine.
I could probably go into a long, LONG rant over why Whitey is racist towards every nationality and ethnicity under the sun, and probably go into some detail over why everyone hates Whitey, but suffice it to say that my beginning statement says it all. Most Stereotypes have at least SOME kernels of truth hidden within based off of certain events in History, but their overblown nature makes them difficult to accept. Religion is also a BIG instigator of a LOT of racism, far more than skin color could ever, EVER hope to come close to.