When a black man robs me or beats me up, I have recourse. When a cop does so, I don't. I don't fear black men because, even if they are more likely to harm me, the power dynamic is very, very different. If any random black man had special power over me, I would be afraid of any that hadn't earned my trust. (Men typically do have special power over women, and as a result, we insist that women need to avoid walking alone at night, not dress provocatively, carefully watch their drinks in bars, not wear their hair in a ponytail when running, have their keys ready when they approach their car in a dark parking lot...always be ready for an attack.)

So, yes, black men may rob and beat up people at a higher rate than cops, but killing is another thing: ~1000 killed by police in 2015[0][1] 765,000 police with arresting powers[2] (I assume we can ignore the bureaucrats.) = ~765 police per police killing.

42 089 131 black/AA people in the US (2014)[3] Assume 50% males: 21 044 566 2,695 murders committed by blacks in 2014.[4] 90% of homicides committed by males.[4] => 2426. => 8675 black men per murder by black men.

So police kill at ten times the rate of black men. (Major caveats: killed != murders; I didn't exclude black children, and it might be easier to avoid being killed by a police officer.)

[0] http://fivethirtyeight.com/features/a-new-estimate-of-killin... [1] http://killedbypolice.net/ [2] http://www.bjs.gov/content/pub/pdf/csllea08.pdf [3] http://quickfacts.census.gov/qfd/states/00000.html [4] https://www.fbi.gov/about-us/cjis/ucr/crime-in-the-u.s/2014/...