Moreover, there’s essentially no relationship between the number of police officers in a municipality and crime levels.

That’s not quite right. The linked article notes:

While multiple studies examining the effect of no police — for example, police strikes (Andenaes, 1974; Clark, 1969; Russell, 1975; Sellwood, 1978; cited in Sherman and Eck, 2002) — show that crime will “skyrocket” in these rare circumstances, studies that examine increases in already-existing police forces do not find significant decreases in crime.

In other words, there is a relationship, but it’s not linear. The studies show that some police are necessary, but at some point adding police does not reduce crime. That finding offers no basis for the claim that the purpose of policing is not to prevent crime. The purpose of over-investing in police may not be crime control, but on that point, Mr. Rahmani contradicts himself:

Remember: all of these studies control for crime levels. This means that White residents demand more policing not because the crime rate is actually high, but because they incorrectly perceive communities of color to represent a criminal threat.

Here Mr. Rahmani seems to be saying that the purpose of the additional policing is to prevent crime, but it’s just not necessary. If we replace “incorrectly perceive” with “dishonestly claim,” Mr. Rahmani’s thesis is supported. But we can’t make that substitution based on the literature. In fact, we cannot really infer whether “incorrectly perceive” or “dishonestly claim” more accurately describes what’s actually happening. The data don’t reveal the motivation for the excess policing. They only reveal that the necessary number of police — a number Mr. Rahmani’s cited source says is greater than zero — has been exceeded.

In short, there may be some fat in the police budget, and there certainly are too many DWB traffic stops. These are bad things. But this new assault on the origins and purpose of “policing” per se is completely unfounded.