I have stayed my objections to this phony and unevidenced line reasoning, and stand by that. But even if it were true...
If the only way the police can think of to stop unjustly executing citizens is to "withdraw" and stop policing altogether, that is strong evidence that BLM was correct to criticize American policing in the first place. Personally, I'll take a momentary bump in the murder rate if it is the price of re-establishing the rule of law and the fundamental rights of citizens. Ordering the police not to murder people should not "reduce morale", and if it does, we need new police or no police. What good is it to have peace at the cost of terror?
I'm not especially convinced that the police prevent murders at all. If we're so convinced that correlation always proves causation, what does it mean that the areas the police patrol most heavily also see the most murders? If they see their job as stopping murders from happening, they clearly aren't very effective at doing so. Nor do I think they do see that as their job. At least around here, they usually show up a half hour after the murder, to shoot the family dog and arrest folks. Never heard of a police officer stopping a future murder from occurring.
A quibble here: I think that police DO in fact help prevent murders and other homicides in certain situations, namely in cases of domestic violence and DWIs. Domestic violence is known to increase in intensity and violence over time. By arresting the perpetrator of violence, at the very least it buys the victim some time to escape, to make plans to escape, to gather resources and get help to leave --something that takes multiple tries, on average.
I think that arrests for DWIs helping to prevent homicides is pretty obvious. That's the reason it is illegal to drive with a BAC over the legal limit: driving under the influence puts everyone in your vehicle and everyone on the road (or nearby sidewalks) at risk of serious injury or death.
I live in a not very big town and it is very easy to see the jail census at any given time. Of the 21 individuals currently incarcerated in the county lock up, one has been sentenced for his offences and I would assume will soon be transported to whatever facility he was sentenced to. There are 4 other individuals who are being held on DWI charges and 6 on domestic assault charges and/or violating an order of protection. Almost all of the cases, including the ones I have mentioned include charges re: alcohol or drugs.
This is just a usual week in the life of my town. Probably every single town in the US.