Do Androids Dream of Electric Sheep

My reaction to the first nine chapters in "Do Androids Dream of Electric Sheep", by Philip K. Dick was that I found the storyline to be very interesting. I enjoyed the story, because I enjoy reading a lot of science fiction and seeing the different scenarios that are presented in each science fiction novel. Before I took this class, I have never heard of this novel, and did not know that it inspired "Blade Runner". I had only seen the movie once with my family, because it is my dad's favorite movie. I didn't really understand it when I saw it the first time, but I hope to enjoy it more the second time. I was shocked when I found out that the setting of the story takes place in 2019. which is not that far off. According to Rick, it sounds like it takes place after a nuclear war, because the weather is always talking about a fallout. The police in the future seem to be different too, in which the main character Rick must kill androids for some reason. I don't get why Rick must kill the androids if they are not hurting anyone else. Is this because the people are afraid of the androids becoming more intelligent than humans?