For two reasons, she is a THREAT to THEM.
And here are the two reasons.
Condoleeza Rice rising to the TOP of the country, then shows that with hard work it can be done, therefore it forces those critics to actually work HARDER in their own fields... and that is something they don't want to do because of their patent slothfulness.
Secondly, once she DOES make it to the top of the American system, it so totally takes away one of their biggest bitching and whining points as they tried to build the victimhood-based 'Community of Neverending Entitlement': That "you can not make it to the top if you are Black, due to racism in America".
This throws out one of their arguments and they are left with little defense. So, Condoleeza Rice symbolizes a big THREAT to their arguing points, and their own excuse for existence.
They also lost their arguing point when they claimed "Minorities" in this country have it bad and cannot succeed, until certain "minorities" like Asians came over as immigrants, penniless refugees, what not, and started to compete with, overtake and then eventually sweep the floor with lazy African-Americans, in academia, work, professions, etc. across the land, also taking such "minorities are victims!" arguments away from the Welfare Lobby. That is why they so often equally hate Asians as well as the Condoleeze Rice's of the world. They are uncomfortable and jealous. Threatened. It shatters everything they stand on and lights an uncomfortable fire underneath their own excuse-making and whining asses.