The Texas utility district appealing to the Supreme Court has no history of racial discrimination; it was created long after 1965. If preclearance is important, let Congress apply it to all the states. If it's not, why burden states and localities for misconduct that almost entirely ceased soon after 1965?
The New Haven firefighters were denied their promotions because, the city of New Haven claims, it feared that the promotion tests would be challenged under a 1971 Supreme Court decision raising a presumption against tests that have "disparate impact" on blacks and whites. That presumption made empirical sense in 1971, when many employers used any stratagem they could to avoid hiring and promoting blacks. But those days are mostly gone, too. The city of New Haven wants to promote blacks. That's why it denied the white and Hispanic firefighters the promotions they had earned on a test the city paid thousands of dollars to develop as fair and racially unbiased.
Similarly, most employers these days want to hire and promote blacks, both to prevent bad publicity and to avoid lawsuits -- and because the vast majority of Americans today want to be fair. But fairness, as the New Haven case shows, inevitably produces disparate impacts.
Talents and abilities are not distributed evenly among people whom we insist on categorizing as white, black, Hispanic, and Asian and Pacific Islander. The Supreme Court's 1971 disparate impact standard, like the Voting Right Act's 1964 standard for voter turnout, was fashioned at a time when racial discrimination was exceedingly common and was pursued cunningly so as to escape legal detection.
That is not the America we live in today. It is not the America that elected Barack Obama president. Retaining these standards today does not prevent racial discrimination, it promotes it -- as the New Haven firefighters can attest.