re: Princeton professor tells Twitter user he can’t discuss music because he’s white

No--this is very racist, not a "little" racist. It is based on a stereotype/prejudice that white people are unable to understand and/or comment on a particular type of music commonly associated with African Americans. (Of course there are many white Americans who listen to this kind of music and are free to comment.)

Imagine a white university professor saying that a black person is unable to comment on a piece of classical music, based on the stereotype/prejudice that black people are unable to understand and/or comment on a particular type of music often associated with European Americans. (Of course, there are many black Americans who listen to classical music and are free to comment.)