Police respond to public opinion (as they perceive it) and political direction. When someone is harassed, I think it is generally not the police themselves who think of this (am I too naive?!). Anyway, if I perceived such a situation, I would attempt to make a non-confrontational appointment with the local police chief and during that brief meeting, I would a) thank the official for taking a few minutes, b) explain what I perceive as possible harassment, without naming any individuals - putting the matter forth specifically but identifying it as a hypothetical situation, c) ask what policies and laws might be applicable; as what the official's view point would be on such a hypothetical situation, and d) thank the official again.
This kind of low-key direct action marks you as a concerned, but not necessarily antagonistic, citizen. It also puts the official on notice that there are members of the community (one of whom has taken the time to step forward!) who are noticing a situation which the official either already knows or should know. If the police actions are truly groundless or based on mis-perceptions, then they are likely to be curtailed. If others in the community are expressing concerns against the individual being harassed, then at least there is now a counter-concern against which to weigh actions. We can express concern without being belligerent - that is ideally an AID to government.