Suppose looters ransack a store when it is closed and are caught on video. Why wouldn't you want facial recognition software to identify them? Do you have a right to privacy when you break into a building? You can support some uses of facial recognition without wanting it to be used to say ticket people for jaywalking.
Edit: just to expand on this, here's a press conference from earlier today (sorry about the poor sound): https://twitter.com/DarwinBondGraha/status/14001715920642416...
Here, Oakland, California's Chief of Police admits that police claims about molotov cocktails and crowd demographics that were used to justify the deployment of tear gas and rubber bullets against protesters a year ago actually had no basis in fact. The Chief explained that he received information to that effect via the radio, and then went out and repeated it to the public (via the media) without making any effort to vet its accuracy. (For clarity, he has only been police chief since February; at the time last year, he was a acting as a spokesperson for the department). It's arguable that the decision to deploy tear gas escalated the protest into a full-fledged riot; even if you don't think so, it certainly misled the public about the behavior and composition of the protesters, inevitably impacting policy debates and so on.
I feel this is a good example of why the police cannot be trusted with facial recognition tools; false claims can be used to to designate large numbers of people as criminal suspects, and that suspect status can then be leveraged to intrude upon their rights. Were California's interim prohibition on facial recognition not in place, chances are that it would already have been deployed to identify large numbers of legitimate protesters on the basis of initial false allegations (ie, lies) made by individual police officers. 33 officers have since been disciplined and no doubt civil litigation will delve deeper into this, but at present the police officers who were disciplined do not have to be identified, despite the fact that they were quite happy to lie in order to violate the rights of that same public.
https://www.ktvu.com/news/oakland-police-chief-apologizes-is...