Because they commit more violent crimes than any other race (despite being only 13% of the population)
===More blacks are shot and killed by police than any other race.=== i do not think that american police is racist they just shoot to kill based on their approved rules of engagement (which imho should be changed) Blacks juts commit more crimes and therefore fell victim to the police actions mopre often if it would be Whites or Asians with the same crime statistics, then it would be them who would be more killed unfortunately both side of the issue do not want to recognize this fact instead backs pushing - racism issue, and police supporters pushing the need to protect the public...both approaches are not really related to the reality on the ground public can and should be protected by the police with the different set of rules of police engagement (especially lethal)
Black people are just plain scary to the Police because of all the gangs and shootings and crime they cause.