First, the NAACP hasn't even agreed with everything Obama said so the idea that they support him on this just because he's black is beyond stupid.
Second, the black population, like the rest of the country, has grown increasingly more supportive of gay marriage. In fact, according to the poll that has been posted several times and you've ignored, 53% of blacks support Obama's statement on gay marriage. Therefore, it's not surprising that the NAACP is growing the hell up like the rest of the country.
Third, the NAACP is not about gay marriage. It's about civil rights and black-specific issues like hate crimes and housing discrimination. The idea that they can't support SSM and still represent much of the black population is beyond nonsensical as is the idea that the black population is monolithic which you apparently seem to think it is.