A high false positive rate doesn't mean much on its own. The real question is what is the point of detecting gunshots? If you are trying to decrease response time to real events, you want to be minimizing your false negatives, and increasing false positives to do so is likely a good strategy. Similarly if you want to use it in conjunction with other data collection, it's probably better to have false positives than false negatives. Of course a more accurate system, with both fewer false positives and false negatives, is always desirable, but the perfect is the enemy of the good enough.

The only reason false positives would be an issue is if you had some better method of identifying where resources ought to be allocated, and instead you were going after these false leads. If the cops had a better system they were being prevented from using, I doubt they'd be arguing to to keep this one in place, and the critics would probably mention it.

I'm not saying this system is worth whatever it costs, indeed the value prop of detecting gunshots seems rather low to me, but the particular argument made in this article is poor.