I think it is important to remember this part of MLK’s speech:
I have a dream that my four little children will one day live in a nation where they will not be judged by the color of their skin but by the content of their character.
Unfortunately, there is a tendency to confuse judging the content of character with the judging of other things like skin color.
This is a feedback problem. The reactions we get from how we behave are feedback that signal when our behavior is acceptable and unacceptable to others.
If it is made easy to believe that changing our behavior will not change the reactions we produce in others when we behave unacceptably, because we attribute their reaction to something else (like skin color), then we are less likely to change our behavior.
In his book, Black Rednecks and White Liberals, Thomas Sowell traces the origin of the collection of behaviors that we recognize today as the ‘thug’ and ‘redneck’ cultures. He hypothesizes that these are evolved versions of the same culture with the same origin.
He also shows that both of these cultures were waning in American society through the first half of the 20th century, due to normal societal feedbacks that encouraged politeness, productivity, self-reliance and cooperation. However, the introduction of the welfare state reversed this course among both blacks and whites, because it enabled folks to get by without adopting these virtues.
Sowell also shows, remarkably, that the behaviors commonly associated with these cultures tend to produce the same reactions in others no matter the skin color of the person practicing them.
I recommend reading it.