Is the logical conclusion to this line of thought that any fewer deaths from police violence justifies a metropolitan area falling into socio-economic collapse?
Overall deaths seems like the correct metric.
If a metro area becomes a literal Gotham City (ie drug and crime completely integrated into daily life) then the outcome is decades of lost human experience across hundreds of thousands (millions?) of people.
Addressing police brutality is one hard to solve problem, but cameras and other initiatives seem to be helping. But your city turning into a crime haven creates thousands of problems, and may not be able to solve.