Yes that is a real criticism against Waze. The thought is that the "show where the cops are" feature can be used by those who wish to assassinate cops (by finding them when they are alone I guess).
There is a movement (it's currently trending on Facebook - so there are plenty articles to read there) that is trying to force Google to remove the offending data. The problem is, to anyone's knowledge, there hasn't been a single case of "officer assault" linked to Waze data.
It does sound silly, as cops are not hard to find. I seriously doubt a would be cop killer needs to consult an app when looking for a cop to kill.
I think it's more likely to be used on the commonplace to avoid areas with police -- either for the traffic ticket dodger, or for mugger's, home invader's, etc...
The obvious conclusion being that the feature must be removed (obvious to a certain Orange country sheriff at least). http://www.npr.org/blogs/thetwo-way/2015/01/28/382013185/off...