When did being brown become not black enough?

I was recently talking to one of my little cousins,who attends middle school. She said a hispanic classmate asked her what C.O.M.P.T.O.N stands for. My cousins response was the city where she lived. Her classmate said no, it stands for "City Of Mexicans Pulling Triggers On Ni**ers". Surprised at this comment my cousin walkled away and began to cry.

I was taken off guard when asked to counsel my little cousin on this matter. It is hard enough growing up "black" in America; add being a female to the equation and chance the for success has decreased dramatically. Not to mention the misconception that since you are black you probably grew up fatherless in the ghetto on welfare, is never far from the definition of who you are as a person. Or our society sees you as the exceptable Negro, the small percentage of African-Americans who are educated and successful. The United States of America is supposidly known for its diverse and accepting nature. Even current politicians point out over time the drastic measures taken to improve race relations have been successful. Is this true? In my opinion, the only variable that has changed is time. Are Americans, as a whole, so worried about being politically correct in public that we forget our children listen behind closed doors.
Either way, when did teaching children tolerance become an act of lip sevice.

When did the relationship between Hispanic and African-American cultures become so hateful, and what, if any, solutions can be implemented to correct this problem?