The premise of this question is false. I object to the harassment of anyone, regardless of the color of their skin. Who would object to preventing the harassment of people with black skin, and why?

There's a massive and historic problem of black-skinned people being harassed (and much worse) by police and civilians. The evidence is overwhelming. Therefore, we need to put great effort into solving it.

The idea that there is a competition between races is not only absurd but well-established to be highly damaging; the results are very bad for everyone. Stopping the harassment of black-skinned people helps everyone. If there's a competition, it's the hateful vs. the great majority who are civilized, regardless of skin color (or religion or sexual preference or country of origin or anything else). I'm on the side of the civilized. If we built a wall to keep out the hateful, think how many problems would simply disappear.