It makes sense for police departments to take advantage of surplus military vehicles, supplies and weapons.
First of all, this equipment is nearly brand new and would be destroyed if police departments did not acquire them. We are talking tens of billions of tax dollars and decades worth of high-end technology that would otherwise go directly in the incinerator.
What's more, starting with the equipment: Helicopters, infrared and night vision scopes and tools are all assets that police departments can train their officers to use. Police work day and night; to be able to have the tools to train in, and actually operate in, nighttime scenarios with the advantage of sight would indisputably result in higher apprehension rates.
Further, providing a department with a helicopter not only creates another job if they don't already have a pilot, it also cuts the time of a search and rescue mission. Also, it lessens the danger to the motoring public if used in pursuits, it's much easier to watch from above and much less threatening to the offender.
Regarding rifles, handguns, semi-automatic and fully automatic guns: The police should have access to a host of weapons, minimally, an arsenal comparable to that of the criminals they face. A cop should never have to die in the line of duty because he was outgunned.
Regarding mine resistant ambush protected (MRAP) vehicles, and other armored and non-armored military vehicles: While it's true some of these vehicles may not be necessary for everyday patrols, and they may sit unmoved 364 days out of the year, that one day they have to use it, I will sure be glad it's there. This theory is similar to car insurance or having a concealed weapon; one has those things in hopes never to use them, but sleeps good at night knowing they are there.
We are in a very volatile society. Many things can make these very items a necessity - natural disaster, fire, police pursuit, rioting, a hostage situation, an active shooter situation, etc.
I don't want to be that community where after something happens, everybody looks back naively and says what could we have done differently.
Safety is absolutely proactive. Anticipate and prepare, then the police, the individual and the community can properly react.