The problem with fixating on the police is that it distracts us from just about everything else activist-orientated.
Yes, I know the activist explanation: that the police are a part of the larger state apparatus -- and often the public face of that apparatus through programs like community policing -- that works to oppress the marginalized of society.
The danger here is that police become the low-hanging fruit when challenging the state.
Because the police...well, are the police. They are the first layer of insulation the state uses to protect itself from citizens in revolt. Anyone studying political science or has been to a protest knows this.