Joi : I missed you, baby sweet. How was your day, hm?
K : It was a day
Joi is K's artificial intelligence girlfriend and although she cannot feel emotions in the same way that a human can, she is programmed with the ability to make the correct overtures of romance and because of this the conversations that the two have sound very much like the conversations that a human boyfriend and girlfriend might have.
This would be appropriate in a different setting, say, if K had come home from working in an office, or from a vacation day fishing with buddies, but his job is that of a blade runner, and he is essentially a police officer who kills deviant replicants. K does not enjoy his job, hence his lackluster reply to Joi's innocuous question.
Every leap of civilization was built off the back of a disposable workforce. We lost our stomach for slaves unless engineered. But I can only make so many.
Wallace is prone to making declarations that are extremely unpalatable, and this is one of them as it implies that humans only object to slavery because it exploited living humans; now that there is a way to exploit replicants, or artificial intelligence beings, nobody seems to have an ethical issue with it. His point is that the concept of slavery is not something that humans find entirely unpleasant, and this is why he has become so successful. Humans like to have someone working for them, someone they can enslave and force to work whenever they tell them to, someone with no other options. Wallace's assertion is that slavery is an acceptable concept to humans as long as they can come up with a way of taking the actual human element out of it.
He also suggests that there is soon to be a shortage of slaves because he just cannot keep up with the demand. Although he has done a good job of producing at the rate of consumption, demand is increasing and he is therefore worried about the implications of people wanting replicants that he cannot produce.
