The last part of your post is the problem, not the black pimp, so I'm in full agreement with you here.C'mon, 'JIM' was Superman. As in "Excuse me White man, that is one striking attire you have on that even as I- a Pimp lol have never seen outside of a comic book. Might you been in need of mental health services?" Then he takes off in the air and you get your 'whoo'.
In the 70's if you needed to get a random white dude's attention for say, a light for a cigarette or the time, you might have used 'Jim'. As opposed to 'Jack' where it might have been for a more, uh curt greeting as it was. I feel that's going a little hard at the idea that was a cruel jab on some level I'd say. In that world no one knows what a Superman even is, the reaction, even if you disagree with the messenger, is pretty genuine. There's a mention of Rex Reed at some point in this one or one of them. Metropolis was representing New York in the 70's and suffice to say, there was a certain element that was much more pervasive than what Manhattan has looked like for the last 30 some odd years. That's to say there was about a 100% fewer sex shop elements in the middle of it. I wanna say that was, **** without looking it up, they guy that played in Uptown Saturday Night that was head of the other gang opposite of John Amos. He's been in a lot of stuff at the time. He was the Jamaican in Predator 2 I think. Damn I can't remember his name off the top of my head. Watch it not even be him... anyway.
You do have a point in that's likely the only brotha with a speaking part in the film. I feel there's one walking in the background of the Daily Planet newsroom in a Margot Kidder shot.