This is a bad decision. It reminds me of how some people here in Toronto a few years ago who posted on Twitter where police were conducting roadside blood alcohol tests.
Speeding excessively is a public health risk. That is indisputable. What the speed limit should be is another question but to alert others who could be breaking the law is wrong.
If a police officer went into an internet chat room (I think they still exist) posing as a minor to find out who the perverts are and somebody else says that so and so is a cop I would hope that we can all agree that would be wrong.