The Reverend Al Sharpton has emerged from several months of uncharacteristic silence to launch into his first challenge to Mayor Bloomberg. His ire is directed at the mayor’s expected appointment Monday of a criminologist and former policeman, James Fyfe, to a position overseeing the training of police officers. Rev. Sharpton has chips to cash with the mayor, having helped him to gain office by working to suppress the black turnout for Mark Green. But Mr. Bloomberg has much to lose and little to gain from this first confrontation, which will do much to shape public perception of the administration’s policies on race. This confrontation will be mainly symbolic, yet highly significant. It is the equivalent of pattern bargaining. Anything the mayor concedes now, he will be expected to concede again the next time Rev. Sharpton takes issue with a policy decision.

Mr. Fyfe has a distinguished record as a criminologist, and little patience with bad, let alone brutal, policing. Rev. Sharpton’s objection to him comes from Mr. Fyfe’s decision to testify — without accepting a witness fee — for the defense in the trial of the police officers who killed Amadou Diallo. Mr. Fyfe stated under oath that the officers were following the NYPD’s procedures, and that those procedures were badly flawed. The Diallo family, he said, should sue in civil court, but were not the victims of purposeful brutality, premeditated or otherwise. Mr. Fyfe is no knee jerk defender of police, however. He worked with the prosecution against police officers in the Rodney King case, and against racial profiling in New Jersey. The irony is that Rev. Sharpton has been talking about backing off from criticizing the police force at large. His grandstanding against Mr. Fyfe, however, suggests he is the same old Rev. Sharpton. He is seeking to maneuver the new mayor into a dangerous dance. The right step for Mr. Bloomberg is to follow through with his appointment of Mr. Fyfe. Or he will end up being led by Mr. Sharpton, and he and the city will suffer.