Lots of things attribute to racism. Probably a main source is a history of racism that have attributed to white folks for quite some time.
White folks have accomplished a lot, and with success often a superiority complex or grand ego follows, and when a culture has succeeded and held a status of power over other countries/cultures for so long, it's embedded in them to feel that anything other than themselves as inferior.
America's most powerful is still dominated by the white race. All the pioneers of science, construction, reform, practically everything that made America was LEAD by white people, with all other races just major contributors from the 'lower' end of the revolutionary spectrum. With such success gives that perception of 'superiority', and it begets the racism that runs rampant even today.
Such a status is hard to let go of course. With other races slowly making their mark in power; Obama as president, more races claiming the title of wealthy in America, and foreigners supposedly 'taking over' the desired high income jobs, it's ruining the 'white dominated' utopia that was the status quo for many decades.
SO when you dislike the outlook of losing 'control' you tend to start looking at the faults of those you hold contempt for.
So suddenly statistics of criminal behavior, intelligence, and any other attributes are revealed to ridicule and degrade races to continue to make their race look 'better' and more 'appropriate' to run society.
That's what's happening now. Now that other races are busy calling them racist, and through programs to accommodate them they've garnered better opportunities and suddenly becoming 'competitive' so to speak in the ultimate American dream of success, white folks have had to resort to more passive aggressive means such as this 'reverse racism' or 'race card' BS to show that other races should be 'happy' with the fact they are no longer being revoked of their rights (at least by perception), and should rather feel as equals now regardless of race.
Only reality though, is that as long as media and the country continues to perpetuate other races' negative sides and show that they aren't 'capable' of receiving assistance for those in poverty, nor any REAL opportunity to gain the opportunity of success as the race in 'power', the ugliness of racism will continue to exist.
It's like they're saying "Okay, we took away everything from you and made sure you stayed as stupid as possible to be below us; then we decided it's not ethical to do as such, so we'll just stop doing it and expect you to just get up and be like us....even though your culture was given no decent education, was politically screwed over for any type of corporate success, and oh yea we'll empower your mediocre successes based on stereotypes to make you think you're intelligent like us...but really you're just worth what WE think you're actually good at. Why are you guys calling us racist?"
Thankfully even amidst racism folks still work hard to get their success, others fall victim to the long term assimilation that they are still considered inferior, and as inferior should not have hopes of even TRYING to succeed, but to accept their stereotypes and make do with what they feel they're 'worth'.
Those who succeed ironically are 'accepted' but in some ways 'unlike' their own race but the race in power (white)....but those who don't are deemed THAT race and so to be a civilized adult you still need to 'be like white people'; otherwise you're just another different race that is inferior and incapable of contributing to society.
THAT'S the largest problem with the racism, and that's why so many white people are still considered racist, which then makes black people out to be the 'dumbest, violent race in America'.
That lil exerpt from Django with Leonardo DiCaprio's little scientific BS about comparing head/brain sizes of slaves to prove they were MEANT to be slaves? Yea not very far from the reality that is today.
my 2 cents.