Thats not the point. The point is that its an example of where you technically have nothing to hide, but most people wouldn't want it anyway. The Police shouldn't be monitored because "They must have nothing to hide" because thats the same reasoning they use to get people to surrender their rights.
The "on employer's time" makes much more sense. They're here to serve the public, so the public should therefore be able to make sure they are doing just that, no more, and no less.