Not because white people are worse than black people about race but because whites are in the majority, and therefore the behavior of whites has a much bigger influence on hiring practices and so forth and so on than the behavior of African-Americans. This reminds me of the leftist cant that only white folks can be racists since only white folks have power. What Dean is saying is not quite that bad, but it is in the same spirit.
It certainly highlights the double standard that the media has about racism.