how can you question if Obama is black or not?

i'm sick of the fools on BTR still debating whether or not President Obama is black or not. Can you believe this? I am totally shocked. first of all, why does it matter? And second of all, if Obama would have been alive during slavery in American, he would have been in chains right next to the ancestors of these black btr hosts who question his race...is that not black enough?.....let's talk about this...