The media and the public see different ethical dilemmas for police officers than the officers see for themselves. Why?
To get a good answer to this, you should tell us a bit more about what ethical dilemmas the two "sides" see for police officers. As it is, we have to sort of guess at what you are talking about.
I believe that the police see different ethical dilemmas because they are in a very different situation than the media and the public are. The media and public are not dealing with the people that the police deal with. The police deal with criminals and possible criminals much more than most of us ever will. They also tend to be in some amount of physical danger much more often than most of us ever will be. Therefore, their vision of the ethical dilemmas inherent in their jobs will be much different than public or media visions of those dilemmas.