1) There have been a few white male presidents before Barack Obama, in case you didn't know.
2) Many people voted for Obama at least in part because he was black, including myself, because they felt it was time to demonstrate we could and should elect a non-white-male president.
3) The president is a very special singular office, whereas there can be an almost unlimited number of coders. Affirmative action for the role of president or elected political office doesn't make a lot of sense (unless it's done by choice of the electorate.)
4) Indeed Barack Obama is a role model for black men. He showed that a black man (and a non-white-man) CAN be president, something hardly anyone thought was possible in our lifetime prior to his rise to prominence.
5) While a white man could be a role model for a black girl in some sense, people identify with those who share a cultural and racial heritage.
While on a certain theoretical level, what you say makes sense, it is not true in the actual world in which we exist.