To reiterate, no a black person can't be racist.
I have also heard this...but come on this is some college professor nonsense. My anthropology professor said this years ago and it stuck with me. Racism is only available to those in power. So, by that pure meaning yes a black man in America is more unlikely to have the POWER to be racist. However, while unlikely, it is still both possible. Additionally, as a microcosm of society it is DEFINITELY possible.
Btw the definition of racism that comes up on a Google search is "the belief that all members of each race possess characteristics or abilities specific to that race, especially so as to distinguish it as inferior or superior to another race or races."
But that distracts us from your point of no, a black person can't be racist.
Yes, yes they can. A black person that ends up economically well off (definitely possible with our generation now), educated, etc and is in a position of POWER can be racist (e.g., Uncle Phil from Fresh Prince). That person is in a position of power. They can wield that power with prejudice against people of a different race. That is literally the definition of racism as you define it (prejudice + the power to act on it).
On a less serious microcosm view - Kevin Durant could be a racist. If a bunch of black guys were hooping and KD is there and is respected by that particular community of hoopers he is in a position of power and influence. If some white guy shows up and wants to play and KD ridicules him based on race and perceived ability that is also racism because it simply power + prejudice.
In the hip hop industry I assume this applies as well. The only real difference is that overall white people still hold the majority of power in a systemic way in a lot of America. It is an ingrained belief but there is definite progress through the form of education. We can only look at this generationally, rather than by a few years or decades. In 20 years, when the 5 years old today are grown adults will they be more or less "racist"? The answer is of course they will be less racist. Not necessarily because they are stronger of principle but rather that the systemic privilege afforded white people continues to dwindle.
These isms are simply power + ability to act on it. Girls that want to be engineers feel this in a similar way. It is all around us....but it definitely is improving.
As an Indian kid it was hard for me growing up even in Silicon Valley. My family grew up celebrating our cultural holidays silently and without any true way to express ourselves. Now, as an adult, I see Diwali (one of the main festivals) recognized by the president of the country and it celebrated by many Indians and non-Indians. Life changes, people progress, education prevails. Focusing on the negative only helps fixate on the wrong area of this debate.
If you are only going to look at it in a big picture way of can the average black man be racist then it is still a no. However, that does not mean it applies on an individual or community level.
