I do not believe that all white people detest blacks, but when a white person is a racist, it is usually because of the attitude of white supremacy, which is the notion that white people are above blacks. There is a seed that was planted long ago by our forefathers that blacks should serve white people. Generally, it is the structural organization of black lives, the material conditions that are considered to be exclusive to the race.
Poverty and under-education are correlated with the black culture. White supremacy is founded on the black condition, which maintains and reproduces it. There are often many assumptions made about those who are different.
There are different reasons for this and it may have stemmed from history. It should be noted that whites used to treat blacks as slaves. When the order was given to free all of the slaves, the whites detested the blacks because they immediately lost their main source of income. It seems that white people detest black people mainly because they do not see the need why they have to be more respectful towards blacks.
This is an unfortunate fact in the world right now: you always have to prove yourself worthy of being respected. If you do not show that you are accomplished, this can become a problem in the long run.