First lemme start this off by saying to any AA reading these kinda threads, completely disregard non AA opinions when it comes to racial classifications in America. They are irrelevant to you.
It depends on the race system. In historically French and Spanish colonies, there is a 3 tier race system.
In the US, the Anglo-Saxon race system is a race binary. So historically, people like Fredrick Douglass who was mixed race, was still a slave, fought for abolition, etc.
In 2018 though, people who have one white parent can go either way as far as helping black people goes. Some go harder because of their white side, others identify more with white because of it.
As far as the existence of white people, race mixing (mainly between black men and white women) is not in the interest of white genetic survival. They are about 8% of the global population, and by definition regardless of where you go, only 2 white people can create a white child. If Obama married a white woman, white America would not accept them as white children.