I've heard statistics from some sources as high as 97% of black voters will be voting for Obama, just google for some of it it's out there. Even if they're off and lets say it's only 85%, still.
If 85% of white people voted for McCain, it would be considered racist.
Check your statistics (and your assumptions). Democratic presidential candidates always get ~90% of the black vote; so, it's just unreasonable to suggest that this is because Obama is black. Kerry got ~88% of the black vote in 2004, while Gore got ~90%. Current estimates suggest that OBama has ~91% of the black vote, which is essentially unchanged. In the Democratic primaries, Senator Clinton was doing very well among black voters in polls, until certain incidents in South Carolina.