It never occurred to me that drugs could be... Er, "extracted" by the means showed in the episode. I was highly creeped out and if I were an addict and I suddenly found out that the supply came from the source shown here, I would first vomit, then I would quit.
I think anyone would have that reaction, a person would have to be of very low moral character to not let it bother them... Also, it makes you think, about yourself.
I can't go into detail about this, it would be a major spoiler.
We know that when Mac tells Danny to do something that involves safety, you can expect Danny to find a reason to ignore it, and that happens here, during the discovery period. You just wanna yell, Hey you Idiot! But Danny is such a NY almost stereotype, I know a few guys from NY that would act exactly like Danny would act.
Speaking of Danny and the way you know he has problems letting stuff go, you would not expect Stella to do the same thing. You want to think that Mac won't find out that she went off, and in a way you hope she gets away with it, but knowing Mac and the history of the characters, you know this is gonna be a problem.
Robert Joy has a pretty good spotlight role in this, about time. And (his character) was as disgusted with the situation shown here as I was.