In this theoretical situation of blacks organizing a "blacks-only" prom, it may be true that whites (in the south anyway) would not have any complaint. That is because it supports their segregational beliefs. Blacks-only and Whites-only proms are the same thing. Both represent the goal of restoring a segregated, racist society.
The other stuff you mentioned about individuals making racist remarks is very different. This is speech and thought, not action. If you\'re saddened because you\'re not allowed to call a black person a "Spade" or some more offensive term right after he\'s call you a white honkey redneck cracker in front of a PA system at a national press conference, well you\'ll just have to think back on who enslaved whom, and get over it. It\'s not reverse discrimination, and it\'s not action. It\'s speech, and any inequalities are enforced by social mores, not federal law. There\'s nothing you can do about it except accept it or whine about it. Which would you prefer?