This is an example of a certain kind of fallacy I've been wanting to find a name for, specifically unwarranted assumptions that some (but not other) aspects of the status quo are invariant to a proposed change. In this case, it's the distribution of crime being invariant to the presence of police. The argument 'police rarely stop crimes in progress, therefore they do not present a significant barrier to crime' is not valid because people avoid committing crimes in places where police might stop them. Another example is 'false accusations of assault are rare, therefore we should lower standards of evidence,' which is not valid because false accusations are disproportionately disincentivized by standards of evidence.
This is an example of a certain kind of fallacy I've been wanting to find a name for, specifically unwarranted assumptions that some (but not other) aspects of the status quo are invariant to a proposed change. In this case, it's the distribution of crime being invariant to the presence of police. The argument 'police rarely stop crimes in progress, therefore they do not present a significant barrier to crime' is not valid because people avoid committing crimes in places where police might stop them. Another example is 'false accusations of assault are rare, therefore we should lower standards of evidence,' which is not valid because false accusations are disproportionately disincentivized by standards of evidence.