If you or I use a gun irresponsibly, we go to jail. If the cops use an APC or flash-bang irresponsibly, they usually suffer no consequences. Add this to the “neat toy” factor, and all that military equipment becomes a solution in search of a problem.
The key words in your own sentence are "use irresponsibly"
Its not the gadget's fault its the person using it.
Just like its not the gun's fault, its the criminal using it.
Why do cops even have APCs and flash-bangs? Those are tools of the soldier, not of the police officer. Perhaps I should say, those are tools of oppressors, not of peace officers - and we know which we have by the tools they choose to employ.