Why are many black people called "acting white" if they don't fall into negative stereotypes?

[SOExclusive]

Everything you said links to racism.

Racism means the belief that one group of people is superior in all ways to another group of people.
That means...

---Eating habits
---Fitness
---Socioeconomic status

The racist believe those types of good living conditioned are entitled to them...and only them. If someone not part of their group has these things, they assume that person is a sellout and whats to be like them.
Of course, for their racial prejudice to spread, they need influence right?
Think back in the 50s, where did racist make influential speeches?

Churches, schools, and national television.

It still happens today, only the racist aren't direct with their racial prejudice. Sadly, many people of different ethnic background buy into the generalization they make, thus those generalizations become stereotypes.

A stereotype is a widely held opinion based off of someone or something.
You have a ton of people believing the stereotype, people are going to expect the stereotype from a certain group of people. That stereotype becomes a stigma for that certain group of people.

A stigma is mark of disgrace passed down as a social norm in society. People are expected to live up to their stigma if they are ascribed one. Not living up to the stigma means you want to be different from what is expected of your group.

Thus...we get the concept of black people that don't live up to their stigma want to be like white people as white people are stigmatized as being fortunate, healthy, and nice, while black people are the opposite.