I feel sorry for the 20% because they will be victims; for the 80% — you ought to be careful for what you ask for lest it be granted. Civil wars are, by definition, not civil. Lots of innocents die in them. Outnumbered by nearly 9 to 1, the Black community may learn the meaning of General Custer's last words at the Battle of Little Big Horn: “Where’d all the Indians come from?”
They are not idiots, and it is possible to be outnumbered 9 to 1 and win. The trick is to define some goals and then see if you can achieve them, one way or another. Once you reach those goals, stop - going any further will result in losing the war.
The minority can use riots (which are a low-key civil war) to gain political advantages, financial reparations, preferred treatment, one-time property assignments, release of prisoners, and many other things. The minority does not need to defeat everyone else militarily - it only needs to sufficiently scare the opponent into surrendering. While the minority is indeed faced with more opponents, the minority is willing to fight, but the opposition isn't. Low IQ street thugs are comfortable with murder, rape and theft - and they want it. As Karl Marx said, "they have nothing to lose but their chains." Many of high IQ workers, engineers and administrators will be horrified at the thought that they need to shoot at someone.
This is proven by history, many times over. Revolutions are usually carried out by a small core of dedicated fighters. They may be outnumbered 100,000 to 1, but it doesn't matter if you hold the Emperor hostage and his 100 guards are on your side. The rest of the country will simply read in morning papers who won and who lost. By and large, those 100,000 don't care who sits in the palace, but you very much do. How many armies Londo Mollari took with him against the Emperor Cartagia?