Do we have robocops? Not yet; robotic police is still in the realm of science fiction. Well then, we obviously do need people to go to police academies and become police officers. Who else will do it if people won't? What is the alternative? This is a rather strange question.
I feel this is somewhat of a silly question and doesn't really need to be debated. Of course people "should" be Police Officers. It's a great career to get into, as you can make a difference in your society, and experience new challenges everyday. With the way things are going on today's world, you can not have too many Police Officers out there. Crime is simply never going to stop.
For themselves however robots, are programmed to do only the right thing for example if a police had to save someone he didn't like he would say no however a robot would save them anyway, and robots don't take days off don't get sick and will never stop working anyway