You want to point out the black guy to your friend for whatever reason.Maybe he is dating your sister or goes to your school or something.I know my question doesn't make much sense so let me giev you an example.You area at a party and there is is like 30 white guys and one black guy.The white guy who told you that is overcompensating and trying to look "enlightened," but he ends up just looking foolish. There may be more than one in the room in your example. It's no worse than tall guy, bearded guy, red-headed guy, guy in wheelchair.... however, i *do* think it is a borderline case when you hear people refer to peoples colour when it has *nothing* to do with the issue at hand "this black astrophysist thinks blahblahblah" for example.Unless his or her ethnicity has specific relevance to the story.
It is not neccessarily racist in itsself, but it does have me wondering what your point is. I once referred to a black friend as being black and she let me know that the proper term was African American.
As I told her, I will be happy to use whichever term is excepted - but stop changing it every few years! I overheard a man tell the DJ that the [insert my type of car here] belonged to "that white dude over there." I wasn't offended and can't see how it was racist.