The same kind of unfavourable and threatening stereotypes can apply to some extent just being a man. Or to a kid wearing a hoodie. I suspect that someone looking like a Hells Angel would cause more disquiet in a lift than someone looking like Obama.

But Obama would be identified as being black in such a casual encounter by the same people who might question whether he should be counted as "black" in a political context, and that was the point being made.

It's inevitable that people will be prone to make a provisional judgement about strangers on the basis of stereotypes they have built up, largely in the modern world from the media. Skin colour, and stereotypes related to that, is one factor here, but not the only one.