And where did you get your "facts" from? Source?
http://www.sfgate.com/bayarea/article/African-Americans-cite...
"African Americans in San Francisco are cited for resisting arrest at a rate eight times greater than whites even when serious crimes are not involved, according to statistics drawn from court records."
Here is also a good overall source (but the author has a label on him).
http://www.colorofcrime.com/2016/03/the-color-of-crime-2016-...
If the same cops patrol the same demographic and the same high crime areas it would reason that the same cops (and same type of specific category) will be making the majority of the arrests. Which will skew the mentioned statistic to them.