In the original paper (https://www.ncjrs.gov/pdffiles1/nij/249895.pdf) Rosenfeld actually details two possible versions of the Ferguson effect: de-policing and a lack of confidence in police activities among black communities.

In fact, the Guardian article you linked to calls out the difference between the two versions of the "Ferguson effect" explicitly.

Rosenfeld explores an alternative version of the Ferguson Effect, in which “longstanding grievances and discontent with policing in African American communities” are “activated” by controversial incidents of police violence, and then “chronic discontent erupts into violence”

-- https://www.theguardian.com/us-news/2016/jun/15/ferguson-effect-homicide-rates-us-crime-study

Additionally, Rosenfeld makes very clear in his paper that he hasn't reach any definitive conclusions in any direction, and his research is simply a call for more research, and better data. The only fact that can really be taken from the paper is the increase in homicide rates, that did happen. Beyond that, he passes no judgement.

Lack of confidence in police institutions leads to a clear, well documented solution, with a plenty of research supporting it: "community policing". Which is pretty much exactly the opposite of the "racist policies".