First, no crime was committed. In fact, the DoJ under Mukasey, Bush's appointee, elected to file a civil complaint and did not bring any criminal charges.
Second, the DoJ dropped the case against some of the Defendants but not all of them. With respect to the one defendant that had the night stick, the DoJ got an injunction against him, which was all the relief the Bush's DoJ wanted.
Third, the case was dropped against the other defendants because the DoJ determined that there was insufficient evidence to support the complaint. Specifically, not a single voter eligible to vote at this particular precinct came forward claiming that they were prevented from voting or were intimidated.
Lastly, it is not a crime for black people to hate white people just like it's not a crime for white people to hate black people. The fact that these guys hate white people, while I understand it gives you the vapors, is no reason to prosecute them for anything.