A good parallel is the Harlem Globetrotters. They were so good in the 40's and 50's putting on exhibition games and beating the local teams they played against because blacks were excluded from the NBA. They got all the best black basketball players as a result of that discrimination. Now that blacks dominate the NBA who do the Harlem Globetrotters get? Not the the players with the top ability. They go to the NBA. With colleges, the best blacks go to Harvard and Yale. No need for HBCU.
It goes even further than that. Some black families who've emerged into the middle class actively dissuade their children from attending HBCUs, which are seen as virulently liberal. The emergent black middle class is becoming more and more conservative, and they don't want their kids trapped in liberal educational hell.
Like so many other things, HBCUs have outlived their usefulness in their traditional roles. I personally wish the HBCUs would drop that title (imagine the outrage if the University of Georgia, say, declared itself to be a HWCU) and instead start representing themselves as what they are: an affordable alternative to big name universities, for all racial backgrounds.
I fervently believe in what Dr. King said in his famous speech:
I have a dream that one day this nation will rise up and live out the true meaning of its creed: "We hold these truths to be self-evident: that all men are created equal." I have a dream that one day on the red hills of Georgia the sons of former slaves and the sons of former slaveowners will be able to sit down together at a table of brotherhood...I have a dream that my four children will one day live in a nation where they will not be judged by the color of their skin but by the content of their character. I have a dream today."
My dream is that ALL of mankind, regardless of race, be regarded not by the color of their skin, but by the content of their character. Maybe I'm an idealist - but I think it's an ideal worth fighting for.