“You have your sheep; hell, you can follow the Ascent in your individual life, and when you grasp the two handles of empathy, you approach honorably. Now if you didn’t have that old sheep, there, I’d see some logic in your position. But every family in this building let’s see; around fifty: one to every three apts, as I compute it every one of us has an animal of some sort."
He didn't kill Rachael.
the empathic faculty probably required an unimpaired group instinct; a solitary organism, such as a spider, would have no use for it; in fact it would tend to abort a spider’s ability to survive. It would make him conscious of the desire to live on the part of his prey. Hence all predators, even highly developed mammals such as cats, would starve.
In that elevator at the museum, he said to himself, I rode down with two creatures, one human, the other android...and my feelings were the reverse of those intended. Of those I’m accustomed to feel am required to feel. He also said that he wanted to have sex with her.
When they was in the car Rick decided that he didn't want to kill Rachael because he has empathy for her.