Putting aside stuff about Uncle Joe and his personality, this still comes out as a move with too many negative unintended consequences.
Off-duty cops and plain clothes cops responding to crime-in-progress situations are more likely to be shot than the BG. On-duty cop arrives knowing that there is at least one BG on the scene. BGs are often defined as those who are not cops in uniform who have a firearm in teir hand - regardless of where it is pointed. While the off-duty/plain clothes cop may have their badge displayed those things are pretty small to begin with and appear even smaller when the attention is focused on the firearm in hand as opposed to looking for a badge of office.
Somebody once had the bright idea of making off-duty/plain clothes cops easier to sort out from the BGs.
http://www.dsmsafety.com/ccw.html The fact that they are no longr in business ought to tell you how well that idea panned out in real life. (Police, LEOSA, Security, and even CCW
http://tacticaltupperware.com/?p=865 . Showed up as a flash in the pan, then faded into the vaults of firearms trivia as the answer to "What is stupider than ___?"
Going beyond the safety aspects of the issue is the HR nightmare that "on duty 24/7" policies create. Cops have an impressive history of court cases (local, statewide, federal appeals Circuits and even SCOTUS) dealing with the issue of just what activity is compensible - such as having to show up 30 minutes before the start of shift to attenf roll call, how long they can go without getting a meal break, determining what constitutes the "work week" for purposes of determining when they have to be paid overtime rates, howlong they can be forced to carry comp time without being allowed to use it, and how they get paid for unused comp time (straight time or overtime). Then comes my personal test for determining whether a cop was "on duty" or "off duty" - will they be covered for Workers Comp claims for injuries sustained when out of uniform and "off duty". For giggles, if a cop is "on duty 24/7" are there any limitations on activity, and if not, why not? (If the cop is on duty, shouldn't there be a policy saying they cannot drink alcoholic beverages? Without such a policy you could get a cop under the influence handling a firearm or making other life and death decisions while in a mentally impaired state. Would the department be liable for injuries or violations of rights committed "on duty" but under the influence? Would the cop be held criminally liable if there was a law against handling a firearm when under the influence?)
Uncle Joe got his hands on some converted military surplus M-16s and had to figure out a way to justify having them.
stay safe.