Why are certain sports dominated by black people and others by white?

I think it has to do with the culture and popularity... 1 of the reasons...

Because in certain sports black people will be better than white people

I don’t know but what annoys me is when a sport is dominated by whites, “something must be done” to get more blacks involved, but when blacks dominate , nothing is said.

Why should it be about colour? Who really cares about melanin?

It has nothing to do with skin color, it's all about motivation. A black player will teach his son his own sport, and a white player will teach his son his own sport, and that's how some sports are dominated by white or black players. 

Basically just look at the origins of the sport and which area of society took it more seriously. Basketball and Football/soccer are sports which has very little chance of injury. So for working class people, they ideal sport as the chances of getting hurt and having to miss work is minimal. Also they can be played with very little space and in urban environments. Rugby and American football, the chances are quite high and could only be played by people who could afford to miss work if hurt and require space and equipment to play. Same with Tennis, Golf etc (less on the injury, more around space needed to play).

The richer class is primarily made up of white people. Sports like golf and tennis require expensive equipment and usually a club membership, attracting richer people.

Sports like football/soccer, basketball, baseball, and combat sports can all be played on the street or a field and don't require as much financial investment.