racism = prejudice + power
No. Racism is believing that people's characteristics are determined by their "race". It is a question of intent and degree. Had Durant meant it as "white people shouldn't be allowed in the NBA due to their inferior athleticism" then it would have been racist and unacceptable, because the brown-ness of his face doesn't give him moral immunity. As it stood, it was a tongue in cheek play on the stereotypes thrown in a friendly manner at a colleague.