"But I know that the vote of 9 out of 10 black Americans for the Democratic Party or for leftist kinds of policies just is not reflective of their opinions"

Clarence Thomas is suggesting that the majority of black Americans voting for the Democratic Party or for leftist policies does not properly reflect their true viewpoints. He indicates that most of black Americans may not in fact support the Democratic Party or leftist policies, however are instead voting for them out of habit or tradition. Thomas is recommending that black Americans should be more open-minded and consider other alternatives, instead of merely voting for the very same celebration or policies out of commitment. He is motivating black Americans to believe for themselves and make their own choices, instead of simply following the crowd. Thomas is likewise recommending that the Democratic Party and leftist policies might not be the best choice for black Americans, which they need to think about other options.