In brief, one can't learn about an event by always being inside the event. One has to move inside and outside the event. Giroux's point was that people learn about social class by crossing the borders between classes. People who hang around in one class are less likely than border crossers to recognize what Bourdieu calls the structuring structures of social class fractions.
I don't know where black holes come into this--but I do know that strange things happen to time and space when you're caught in an event horizon. In some way, genres might be like black holes.